diff --git a/README.md b/README.md
index 42b7d725a..73da0a789 100644
--- a/README.md
+++ b/README.md
@@ -452,7 +452,8 @@ Output will be saved with the same name as input SASS file into the current work
     --source-map-root          Base path, will be emitted in source-map as is
     --include-path             Path to look for imported files
     --precision                The amount of precision allowed in decimal numbers
-    --importer                 Path to custom importer
+    --importer                 Path to .js file containing custom importer
+    --functions                Path to .js file containing custom functions
     --help                     Print usage info
 ```
 
diff --git a/bin/node-sass b/bin/node-sass
index f0a548351..f85043271 100755
--- a/bin/node-sass
+++ b/bin/node-sass
@@ -42,7 +42,8 @@ var cli = meow({
     '  --source-map-root          Base path, will be emitted in source-map as is',
     '  --include-path             Path to look for imported files',
     '  --precision                The amount of precision allowed in decimal numbers',
-    '  --importer                 Path to custom importer',
+    '  --importer                 Path to .js file containing custom importer',
+    '  --functions                Path to .js file containing custom functions',
     '  --help                     Print usage info'
   ].join('\n')
 }, {
@@ -55,6 +56,8 @@ var cli = meow({
     'source-comments'
   ],
   string: [
+    'functions',
+    'importer',
     'include-path',
     'indent-type',
     'linefeed',
@@ -227,6 +230,14 @@ function run(options, emitter) {
     }
   }
 
+  if (options.functions) {
+    if ((path.resolve(options.functions) === path.normalize(options.functions).replace(/(.+)([\/|\\])$/, '$1'))) {
+      options.functions = require(options.functions);
+    } else {
+      options.functions = require(path.resolve(process.cwd(), options.functions));
+    }
+  }
+
   if (options.watch) {
     watch(options, emitter);
   } else {
diff --git a/lib/render.js b/lib/render.js
index ae7f0b226..28e41a181 100644
--- a/lib/render.js
+++ b/lib/render.js
@@ -30,6 +30,7 @@ module.exports = function(options, emitter) {
     sourceMap: options.sourceMap,
     sourceMapRoot: options.sourceMapRoot,
     importer: options.importer,
+    functions: options.functions,
     indentWidth: options.indentWidth,
     indentType: options.indentType,
     linefeed: options.linefeed
diff --git a/test/cli.js b/test/cli.js
index fc3c0a1b7..16476e893 100644
--- a/test/cli.js
+++ b/test/cli.js
@@ -400,4 +400,38 @@ describe('cli', function() {
       });
     });
   });
+
+  describe('functions', function() {
+    it('should let custom functions call setter methods on wrapped sass values (number)', function(done) {
+      var dest = fixture('custom-functions/setter.css');
+      var src = fixture('custom-functions/setter.scss');
+      var expected = read(fixture('custom-functions/setter-expected.css'), 'utf8').trim().replace(/\r\n/g, '\n');
+      var bin = spawn(cli, [
+        src, '--output', path.dirname(dest),
+        '--functions', fixture('extras/my_custom_functions_setter.js')
+      ]);
+
+      bin.once('close', function() {
+        assert.equal(read(dest, 'utf8').trim(), expected);
+        fs.unlinkSync(dest);
+        done();
+      });
+    });
+
+    it('should properly convert strings when calling custom functions', function(done) {
+      var dest = fixture('custom-functions/string-conversion.css');
+      var src = fixture('custom-functions/string-conversion.scss');
+      var expected = read(fixture('custom-functions/string-conversion-expected.css'), 'utf8').trim().replace(/\r\n/g, '\n');
+      var bin = spawn(cli, [
+        src, '--output', path.dirname(dest),
+        '--functions', fixture('extras/my_custom_functions_string_conversion.js')
+      ]);
+
+      bin.once('close', function() {
+        assert.equal(read(dest, 'utf8').trim(), expected);
+        fs.unlinkSync(dest);
+        done();
+      });
+    });
+  });
 });
diff --git a/test/fixtures/custom-functions/setter-expected.css b/test/fixtures/custom-functions/setter-expected.css
new file mode 100644
index 000000000..9b67ea9aa
--- /dev/null
+++ b/test/fixtures/custom-functions/setter-expected.css
@@ -0,0 +1,3 @@
+div {
+  width: 42rem;
+  height: 84px; }
diff --git a/test/fixtures/custom-functions/setter.scss b/test/fixtures/custom-functions/setter.scss
new file mode 100644
index 000000000..fbc6116b1
--- /dev/null
+++ b/test/fixtures/custom-functions/setter.scss
@@ -0,0 +1 @@
+div { width: foo(42px); height: bar(42px); }
diff --git a/test/fixtures/custom-functions/string-conversion-expected.css b/test/fixtures/custom-functions/string-conversion-expected.css
new file mode 100644
index 000000000..741d2cb50
--- /dev/null
+++ b/test/fixtures/custom-functions/string-conversion-expected.css
@@ -0,0 +1,2 @@
+div {
+  color: "barbar"; }
diff --git a/test/fixtures/custom-functions/string-conversion.scss b/test/fixtures/custom-functions/string-conversion.scss
new file mode 100644
index 000000000..4e6403f16
--- /dev/null
+++ b/test/fixtures/custom-functions/string-conversion.scss
@@ -0,0 +1 @@
+div { color: foo("bar"); }
diff --git a/test/fixtures/extras/my_custom_functions_setter.js b/test/fixtures/extras/my_custom_functions_setter.js
new file mode 100644
index 000000000..9ec8c24e5
--- /dev/null
+++ b/test/fixtures/extras/my_custom_functions_setter.js
@@ -0,0 +1,10 @@
+module.exports = {
+  'foo($a)': function(size) {
+    size.setUnit('rem');
+    return size;
+  },
+  'bar($a)': function(size) {
+    size.setValue(size.getValue() * 2);
+    return size;
+  }
+};
diff --git a/test/fixtures/extras/my_custom_functions_string_conversion.js b/test/fixtures/extras/my_custom_functions_string_conversion.js
new file mode 100644
index 000000000..3aa4eb8fe
--- /dev/null
+++ b/test/fixtures/extras/my_custom_functions_string_conversion.js
@@ -0,0 +1,8 @@
+var sass = require('../../..');
+
+module.exports = {
+  'foo($a)': function(str) {
+    str = str.getValue().replace(/['"]/g, '');
+    return new sass.types.String('"' + str + str + '"');
+  }
+};