diff --git a/src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/DynamicMethod.cs b/src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/DynamicMethod.cs
index 07ec361a0f7d7..18428b0eb34ad 100644
--- a/src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/DynamicMethod.cs
+++ b/src/coreclr/System.Private.CoreLib/src/System/Reflection/Emit/DynamicMethod.cs
@@ -624,15 +624,18 @@ public override object Invoke(object? obj, BindingFlags invokeAttr, Binder? bind
                 throw new ArgumentException(SR.Argument_MustBeRuntimeMethodInfo, "this");
             }
 
-            public override object[] GetCustomAttributes(Type attributeType, bool inherit)
+            public override object[] GetCustomAttributes(Type attributeType!!, bool inherit)
             {
-                if (attributeType == null)
-                    throw new ArgumentNullException(nameof(attributeType));
+                if (attributeType.UnderlyingSystemType is not RuntimeType attributeRuntimeType)
+                    throw new ArgumentException(SR.Arg_MustBeType, nameof(attributeType));
 
-                if (attributeType.IsAssignableFrom(typeof(MethodImplAttribute)))
-                    return new object[] { new MethodImplAttribute((MethodImplOptions)GetMethodImplementationFlags()) };
-                else
-                    return Array.Empty<object>();
+                bool includeMethodImplAttribute = attributeType.IsAssignableFrom(typeof(MethodImplAttribute));
+                object[] result = CustomAttribute.CreateAttributeArrayHelper(attributeRuntimeType, includeMethodImplAttribute ? 1 : 0);
+                if (includeMethodImplAttribute)
+                {
+                    result[0] = new MethodImplAttribute((MethodImplOptions)GetMethodImplementationFlags());
+                }
+                return result;
             }
 
             public override object[] GetCustomAttributes(bool inherit)
diff --git a/src/libraries/System.Runtime/tests/System/Attributes.cs b/src/libraries/System.Runtime/tests/System/Attributes.cs
index 3dda3f56b3566..6d504c0eeecdb 100644
--- a/src/libraries/System.Runtime/tests/System/Attributes.cs
+++ b/src/libraries/System.Runtime/tests/System/Attributes.cs
@@ -17,6 +17,8 @@
 using System.Reflection;
 using System.Linq;
 using System.Diagnostics;
+using System.Reflection.Emit;
+using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using Xunit;
 
@@ -220,14 +222,34 @@ public static void GetCustomAttributes_Interface()
         }
 
         [Fact]
-        [ActiveIssue("https://github.com/dotnet/runtime/issues/56887)", TestRuntimes.Mono)]
+        public static void GetCustomAttributes_DynamicMethod()
+        {
+            var dynamicMethod = new DynamicMethod("test", typeof(void), Type.EmptyTypes);
+            dynamicMethod.GetILGenerator().Emit(OpCodes.Ret);
+            var action = (Action)dynamicMethod.CreateDelegate(typeof(Action));
+
+            Attribute[] attributes = Attribute.GetCustomAttributes(action.Method, typeof(NameableAttribute));
+            Assert.Empty(attributes);
+            Assert.IsType<NameableAttribute[]>(attributes);
+
+            attributes = Attribute.GetCustomAttributes(action.Method);
+            Assert.Equal(1, attributes.Length);
+            Assert.IsType<MethodImplAttribute>(attributes[0]);
+
+            attributes = Attribute.GetCustomAttributes(action.Method, typeof(MethodImplAttribute));
+            Assert.Equal(1, attributes.Length);
+            Assert.IsType<MethodImplAttribute[]>(attributes);
+        }
+
+        [Fact]
+        [ActiveIssue("https://github.com/dotnet/runtime/issues/56887", TestRuntimes.Mono)]
         public static void GetCustomAttributesWorksWithOpenAndClosedGenericTypesForType()
         {
             GenericAttributesTestHelper<string>(t => Attribute.GetCustomAttributes(typeof(HasGenericAttribute), t));
         }
 
         [Fact]
-        [ActiveIssue("https://github.com/dotnet/runtime/issues/56887)", TestRuntimes.Mono)]
+        [ActiveIssue("https://github.com/dotnet/runtime/issues/56887", TestRuntimes.Mono)]
         public static void GetCustomAttributesWorksWithOpenAndClosedGenericTypesForField()
         {
             FieldInfo field = typeof(HasGenericAttribute).GetField(nameof(HasGenericAttribute.Field), BindingFlags.NonPublic | BindingFlags.Instance);
@@ -235,7 +257,7 @@ public static void GetCustomAttributesWorksWithOpenAndClosedGenericTypesForField
         }
 
         [Fact]
-        [ActiveIssue("https://github.com/dotnet/runtime/issues/56887)", TestRuntimes.Mono)]
+        [ActiveIssue("https://github.com/dotnet/runtime/issues/56887", TestRuntimes.Mono)]
         public static void GetCustomAttributesWorksWithOpenAndClosedGenericTypesForConstructor()
         {
             ConstructorInfo method = typeof(HasGenericAttribute).GetConstructor(Type.EmptyTypes);
@@ -243,7 +265,7 @@ public static void GetCustomAttributesWorksWithOpenAndClosedGenericTypesForConst
         }
 
         [Fact]
-        [ActiveIssue("https://github.com/dotnet/runtime/issues/56887)", TestRuntimes.Mono)]
+        [ActiveIssue("https://github.com/dotnet/runtime/issues/56887", TestRuntimes.Mono)]
         public static void GetCustomAttributesWorksWithOpenAndClosedGenericTypesForMethod()
         {
             MethodInfo method = typeof(HasGenericAttribute).GetMethod(nameof(HasGenericAttribute.Method));
@@ -251,7 +273,7 @@ public static void GetCustomAttributesWorksWithOpenAndClosedGenericTypesForMetho
         }
 
         [Fact]
-        [ActiveIssue("https://github.com/dotnet/runtime/issues/56887)", TestRuntimes.Mono)]
+        [ActiveIssue("https://github.com/dotnet/runtime/issues/56887", TestRuntimes.Mono)]
         public static void GetCustomAttributesWorksWithOpenAndClosedGenericTypesForParameter()
         {
             ParameterInfo parameter = typeof(HasGenericAttribute).GetMethod(nameof(HasGenericAttribute.Method)).GetParameters()[0];
@@ -259,7 +281,7 @@ public static void GetCustomAttributesWorksWithOpenAndClosedGenericTypesForParam
         }
 
         [Fact]
-        [ActiveIssue("https://github.com/dotnet/runtime/issues/56887)", TestRuntimes.Mono)]
+        [ActiveIssue("https://github.com/dotnet/runtime/issues/56887", TestRuntimes.Mono)]
         public static void GetCustomAttributesWorksWithOpenAndClosedGenericTypesForProperty()
         {
             PropertyInfo property = typeof(HasGenericAttribute).GetProperty(nameof(HasGenericAttribute.Property));
@@ -267,7 +289,7 @@ public static void GetCustomAttributesWorksWithOpenAndClosedGenericTypesForPrope
         }
 
         [Fact]
-        [ActiveIssue("https://github.com/dotnet/runtime/issues/56887)", TestRuntimes.Mono)]
+        [ActiveIssue("https://github.com/dotnet/runtime/issues/56887", TestRuntimes.Mono)]
         public static void GetCustomAttributesWorksWithOpenAndClosedGenericTypesForEvent()
         {
             EventInfo @event = typeof(HasGenericAttribute).GetEvent(nameof(HasGenericAttribute.Event));
diff --git a/src/mono/System.Private.CoreLib/src/System/Reflection/Emit/DynamicMethod.cs b/src/mono/System.Private.CoreLib/src/System/Reflection/Emit/DynamicMethod.cs
index 0fb360164f4f2..21ee166a5a63b 100644
--- a/src/mono/System.Private.CoreLib/src/System/Reflection/Emit/DynamicMethod.cs
+++ b/src/mono/System.Private.CoreLib/src/System/Reflection/Emit/DynamicMethod.cs
@@ -247,16 +247,17 @@ public override object[] GetCustomAttributes(bool inherit)
             return new object[] { new MethodImplAttribute((MethodImplOptions)GetMethodImplementationFlags()) };
         }
 
-        public override object[] GetCustomAttributes(Type attributeType,
-                                  bool inherit)
+        public override object[] GetCustomAttributes(Type attributeType!!, bool inherit)
         {
-            if (attributeType == null)
-                throw new ArgumentNullException(nameof(attributeType));
-
             if (attributeType.IsAssignableFrom(typeof(MethodImplAttribute)))
-                return new object[] { new MethodImplAttribute((MethodImplOptions)GetMethodImplementationFlags()) };
-            else
-                return Array.Empty<object>();
+            {
+                // avoid calling CreateInstance() in the common case where the type is Attribute
+                object[] result = attributeType == typeof(Attribute) ? new Attribute[1] : (object[])Array.CreateInstance(attributeType, 1);
+                result[0] = new MethodImplAttribute((MethodImplOptions)GetMethodImplementationFlags());
+                return result;
+            }
+
+            return (object[])Array.CreateInstance(attributeType.IsValueType || attributeType.ContainsGenericParameters ? typeof(object) : attributeType, 0);
         }
 
         public DynamicILInfo GetDynamicILInfo()