diff --git a/.travis.yml b/.travis.yml
index 5fa7c225c..d18c084dd 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -20,7 +20,8 @@ cache:
 
 script:
   - bundle exec rake ci
-
+after_success:
+  - codeclimate-test-reporter
 env:
   global:
     - "JRUBY_OPTS='--dev -J-Xmx1024M --debug'"
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2fba2b018..10e7eb0b8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,10 @@ Fixes:
 
 Features:
 
+- [#1968](https://github.com/rails-api/active_model_serializers/pull/1968) (@NullVoxPopuli)
+  - Add controller namespace to default controller lookup
+  - Provide a `namespace` render option
+  - document how set the namespace in the controller for implicit lookup.
 - [#1791](https://github.com/rails-api/active_model_serializers/pull/1791) (@bf4, @youroff, @NullVoxPopuli)
   - Added `jsonapi_namespace_separator` config option.
 - [#1889](https://github.com/rails-api/active_model_serializers/pull/1889) Support key transformation for Attributes adapter (@iancanderson, @danbee)
diff --git a/docs/general/rendering.md b/docs/general/rendering.md
index 72392dd2b..b75c31938 100644
--- a/docs/general/rendering.md
+++ b/docs/general/rendering.md
@@ -243,6 +243,36 @@ This will be rendered as:
 ```
 Note: the `Attributes` adapter (default) does not include a resource root. You also will not be able to create a single top-level root if you are using the :json_api adapter.
 
+#### namespace
+
+The namespace for serializer lookup is based on the controller.
+
+To configure the implicit namespace, in your controller, create a before filter
+
+```ruby
+before_action do
+  self.namespace_for_serializer = Api::V2
+end
+```
+
+`namespace` can also be passed in as a render option:
+
+
+```ruby
+@post = Post.first
+render json: @post, namespace: Api::V2
+```
+
+This tells the serializer lookup to check for the existence of `Api::V2::PostSerializer`, and if any relations are rendered with `@post`, they will also utilize the `Api::V2` namespace.  
+
+The `namespace` can be any object whose namespace can be represented by string interpolation (i.e. by calling to_s)
+- Module `Api::V2`
+- String `'Api::V2'`
+- Symbol `:'Api::V2'`
+
+Note that by using a string and symbol, Ruby will assume the namespace is defined at the top level.
+
+
 #### serializer
 
 PR please :)
diff --git a/lib/action_controller/serialization.rb b/lib/action_controller/serialization.rb
index 527ed2b61..ea84c6743 100644
--- a/lib/action_controller/serialization.rb
+++ b/lib/action_controller/serialization.rb
@@ -16,6 +16,12 @@ def serialization_scope(scope)
     included do
       class_attribute :_serialization_scope
       self._serialization_scope = :current_user
+
+      attr_writer :namespace_for_serializer
+    end
+
+    def namespace_for_serializer
+      @namespace_for_serializer ||= self.class.parent unless self.class.parent == Object
     end
 
     def serialization_scope
@@ -30,6 +36,9 @@ def get_serializer(resource, options = {})
           "Please pass 'adapter: false' or see ActiveSupport::SerializableResource.new"
         options[:adapter] = false
       end
+
+      options.fetch(:namespace) { options[:namespace] = namespace_for_serializer }
+
       serializable_resource = ActiveModelSerializers::SerializableResource.new(resource, options)
       serializable_resource.serialization_scope ||= options.fetch(:scope) { serialization_scope }
       serializable_resource.serialization_scope_name = options.fetch(:scope_name) { _serialization_scope }
diff --git a/lib/active_model/serializer.rb b/lib/active_model/serializer.rb
index 7d499b909..81beffd7c 100644
--- a/lib/active_model/serializer.rb
+++ b/lib/active_model/serializer.rb
@@ -44,7 +44,7 @@ def self.serializer_for(resource, options = {})
       elsif resource.respond_to?(:to_ary)
         config.collection_serializer
       else
-        options.fetch(:serializer) { get_serializer_for(resource.class) }
+        options.fetch(:serializer) { get_serializer_for(resource.class, options[:namespace]) }
       end
     end
 
@@ -59,13 +59,14 @@ class << self
     end
 
     # @api private
-    def self.serializer_lookup_chain_for(klass)
+    def self.serializer_lookup_chain_for(klass, namespace = nil)
       chain = []
 
       resource_class_name = klass.name.demodulize
       resource_namespace = klass.name.deconstantize
       serializer_class_name = "#{resource_class_name}Serializer"
 
+      chain.push("#{namespace}::#{serializer_class_name}") if namespace
       chain.push("#{name}::#{serializer_class_name}") if self != ActiveModel::Serializer
       chain.push("#{resource_namespace}::#{serializer_class_name}")
 
@@ -84,11 +85,14 @@ def self.serializers_cache
     #   1. class name appended with "Serializer"
     #   2. try again with superclass, if present
     #   3. nil
-    def self.get_serializer_for(klass)
+    def self.get_serializer_for(klass, namespace = nil)
       return nil unless config.serializer_lookup_enabled
-      serializers_cache.fetch_or_store(klass) do
+
+      cache_key = ActiveSupport::Cache.expand_cache_key(klass, namespace)
+      serializers_cache.fetch_or_store(cache_key) do
         # NOTE(beauby): When we drop 1.9.3 support we can lazify the map for perfs.
-        serializer_class = serializer_lookup_chain_for(klass).map(&:safe_constantize).find { |x| x && x < ActiveModel::Serializer }
+        lookup_chain = serializer_lookup_chain_for(klass, namespace)
+        serializer_class = lookup_chain.map(&:safe_constantize).find { |x| x && x < ActiveModel::Serializer }
 
         if serializer_class
           serializer_class
diff --git a/lib/active_model/serializer/reflection.rb b/lib/active_model/serializer/reflection.rb
index 5b4707058..96645bd73 100644
--- a/lib/active_model/serializer/reflection.rb
+++ b/lib/active_model/serializer/reflection.rb
@@ -106,6 +106,10 @@ def value(serializer, include_slice)
       #
       def build_association(parent_serializer, parent_serializer_options, include_slice = {})
         reflection_options = options.dup
+
+        # Pass the parent's namespace onto the child serializer
+        reflection_options[:namespace] ||= parent_serializer_options[:namespace]
+
         association_value = value(parent_serializer, include_slice)
         serializer_class = parent_serializer.class.serializer_for(association_value, reflection_options)
         reflection_options[:include_data] = include_data?(include_slice)
diff --git a/lib/active_model_serializers/serializable_resource.rb b/lib/active_model_serializers/serializable_resource.rb
index 9e03c686d..f67cf2385 100644
--- a/lib/active_model_serializers/serializable_resource.rb
+++ b/lib/active_model_serializers/serializable_resource.rb
@@ -55,7 +55,7 @@ def serializer
       @serializer ||=
         begin
           @serializer = serializer_opts.delete(:serializer)
-          @serializer ||= ActiveModel::Serializer.serializer_for(resource)
+          @serializer ||= ActiveModel::Serializer.serializer_for(resource, serializer_opts)
 
           if serializer_opts.key?(:each_serializer)
             serializer_opts[:serializer] = serializer_opts.delete(:each_serializer)
diff --git a/test/action_controller/namespace_lookup_test.rb b/test/action_controller/namespace_lookup_test.rb
new file mode 100644
index 000000000..dfab02c48
--- /dev/null
+++ b/test/action_controller/namespace_lookup_test.rb
@@ -0,0 +1,149 @@
+require 'test_helper'
+
+module ActionController
+  module Serialization
+    class NamespaceLookupTest < ActionController::TestCase
+      class Book < ::Model; end
+      class Page < ::Model; end
+      class Writer < ::Model; end
+
+      module Api
+        module V2
+          class BookSerializer < ActiveModel::Serializer
+            attributes :title
+          end
+        end
+
+        module V3
+          class BookSerializer < ActiveModel::Serializer
+            attributes :title, :body
+
+            belongs_to :writer
+          end
+
+          class WriterSerializer < ActiveModel::Serializer
+            attributes :name
+          end
+
+          class LookupTestController < ActionController::Base
+            before_action only: [:namespace_set_in_before_filter] do
+              self.namespace_for_serializer = Api::V2
+            end
+
+            def implicit_namespaced_serializer
+              writer = Writer.new(name: 'Bob')
+              book = Book.new(title: 'New Post', body: 'Body', writer: writer)
+
+              render json: book
+            end
+
+            def explicit_namespace_as_module
+              book = Book.new(title: 'New Post', body: 'Body')
+
+              render json: book, namespace: Api::V2
+            end
+
+            def explicit_namespace_as_string
+              book = Book.new(title: 'New Post', body: 'Body')
+
+              # because this is a string, ruby can't auto-lookup the constant, so otherwise
+              # the looku things we mean ::Api::V2
+              render json: book, namespace: 'ActionController::Serialization::NamespaceLookupTest::Api::V2'
+            end
+
+            def explicit_namespace_as_symbol
+              book = Book.new(title: 'New Post', body: 'Body')
+
+              # because this is a string, ruby can't auto-lookup the constant, so otherwise
+              # the looku things we mean ::Api::V2
+              render json: book, namespace: :'ActionController::Serialization::NamespaceLookupTest::Api::V2'
+            end
+
+            def invalid_namespace
+              book = Book.new(title: 'New Post', body: 'Body')
+
+              render json: book, namespace: :api_v2
+            end
+
+            def namespace_set_in_before_filter
+              book = Book.new(title: 'New Post', body: 'Body')
+              render json: book
+            end
+          end
+        end
+      end
+
+      tests Api::V3::LookupTestController
+
+      setup do
+        @test_namespace = self.class.parent
+      end
+
+      test 'implicitly uses namespaced serializer' do
+        get :implicit_namespaced_serializer
+
+        assert_serializer Api::V3::BookSerializer
+
+        expected = { 'title' => 'New Post', 'body' => 'Body', 'writer' => { 'name' => 'Bob' } }
+        actual = JSON.parse(@response.body)
+
+        assert_equal expected, actual
+      end
+
+      test 'explicit namespace as module' do
+        get :explicit_namespace_as_module
+
+        assert_serializer Api::V2::BookSerializer
+
+        expected = { 'title' => 'New Post' }
+        actual = JSON.parse(@response.body)
+
+        assert_equal expected, actual
+      end
+
+      test 'explicit namespace as string' do
+        get :explicit_namespace_as_string
+
+        assert_serializer Api::V2::BookSerializer
+
+        expected = { 'title' => 'New Post' }
+        actual = JSON.parse(@response.body)
+
+        assert_equal expected, actual
+      end
+
+      test 'explicit namespace as symbol' do
+        get :explicit_namespace_as_symbol
+
+        assert_serializer Api::V2::BookSerializer
+
+        expected = { 'title' => 'New Post' }
+        actual = JSON.parse(@response.body)
+
+        assert_equal expected, actual
+      end
+
+      test 'invalid namespace' do
+        get :invalid_namespace
+
+        assert_serializer ActiveModel::Serializer::Null
+
+        expected = { 'title' => 'New Post', 'body' => 'Body' }
+        actual = JSON.parse(@response.body)
+
+        assert_equal expected, actual
+      end
+
+      test 'namespace set in before filter' do
+        get :namespace_set_in_before_filter
+
+        assert_serializer Api::V2::BookSerializer
+
+        expected = { 'title' => 'New Post' }
+        actual = JSON.parse(@response.body)
+
+        assert_equal expected, actual
+      end
+    end
+  end
+end
diff --git a/test/serializers/serializer_for_with_namespace_test.rb b/test/serializers/serializer_for_with_namespace_test.rb
new file mode 100644
index 000000000..5a8a9ed54
--- /dev/null
+++ b/test/serializers/serializer_for_with_namespace_test.rb
@@ -0,0 +1,87 @@
+require 'test_helper'
+
+module ActiveModel
+  class Serializer
+    class SerializerForWithNamespaceTest < ActiveSupport::TestCase
+      class Book < ::Model; end
+      class Page < ::Model; end
+      class Publisher < ::Model; end
+
+      module Api
+        module V3
+          class BookSerializer < ActiveModel::Serializer
+            attributes :title, :author_name
+
+            has_many :pages
+            belongs_to :publisher
+          end
+
+          class PageSerializer < ActiveModel::Serializer
+            attributes :number, :text
+
+            belongs_to :book
+          end
+
+          class PublisherSerializer < ActiveModel::Serializer
+            attributes :name
+          end
+        end
+      end
+
+      class BookSerializer < ActiveModel::Serializer
+        attributes :title, :author_name
+      end
+      test 'resource without a namespace' do
+        book = Book.new(title: 'A Post', author_name: 'hello')
+
+        # TODO: this should be able to pull up this serializer without explicitly specifying the serializer
+        #       currently, with no options, it still uses the Api::V3 serializer
+        result = ActiveModelSerializers::SerializableResource.new(book, serializer: BookSerializer).serializable_hash
+
+        expected = { title: 'A Post', author_name: 'hello' }
+        assert_equal expected, result
+      end
+
+      test 'resource with namespace' do
+        book = Book.new(title: 'A Post', author_name: 'hi')
+
+        result = ActiveModelSerializers::SerializableResource.new(book, namespace: Api::V3).serializable_hash
+
+        expected = { title: 'A Post', author_name: 'hi', pages: nil, publisher: nil }
+        assert_equal expected, result
+      end
+
+      test 'has_many with nested serializer under the namespace' do
+        page = Page.new(number: 1, text: 'hello')
+        book = Book.new(title: 'A Post', author_name: 'hi', pages: [page])
+
+        result = ActiveModelSerializers::SerializableResource.new(book, namespace: Api::V3).serializable_hash
+
+        expected = {
+          title: 'A Post', author_name: 'hi',
+          publisher: nil,
+          pages: [{
+            number: 1, text: 'hello'
+          }]
+        }
+        assert_equal expected, result
+      end
+
+      test 'belongs_to with nested serializer under the namespace' do
+        publisher = Publisher.new(name: 'Disney')
+        book = Book.new(title: 'A Post', author_name: 'hi', publisher: publisher)
+
+        result = ActiveModelSerializers::SerializableResource.new(book, namespace: Api::V3).serializable_hash
+
+        expected = {
+          title: 'A Post', author_name: 'hi',
+          pages: nil,
+          publisher: {
+            name: 'Disney'
+          }
+        }
+        assert_equal expected, result
+      end
+    end
+  end
+end