diff --git a/CHANGELOG.md b/CHANGELOG.md
index 751da693..49b3aab2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@ Features:
 
 - [#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)
 
 Fixes:
 
diff --git a/docs/general/configuration_options.md b/docs/general/configuration_options.md
index e4ef79ae..b83399a2 100644
--- a/docs/general/configuration_options.md
+++ b/docs/general/configuration_options.md
@@ -46,6 +46,7 @@ Each adapter has a default key transform configured:
 
 | Adapter | Default Key Transform |
 |----|----|
+| `Attributes` | `:unaltered` |
 | `Json` | `:unaltered` |
 | `JsonApi` | `:dash` |
 
diff --git a/lib/active_model_serializers/adapter/attributes.rb b/lib/active_model_serializers/adapter/attributes.rb
index 9ddf8516..79ca7b5f 100644
--- a/lib/active_model_serializers/adapter/attributes.rb
+++ b/lib/active_model_serializers/adapter/attributes.rb
@@ -4,7 +4,9 @@ module ActiveModelSerializers
       def serializable_hash(options = nil)
         options = serialization_options(options)
         options[:fields] ||= instance_options[:fields]
-        serializer.serializable_hash(instance_options, options, self)
+        serialized_hash = serializer.serializable_hash(instance_options, options, self)
+
+        self.class.transform_key_casing!(serialized_hash, instance_options)
       end
     end
   end
diff --git a/lib/active_model_serializers/key_transform.rb b/lib/active_model_serializers/key_transform.rb
index 89143cee..d0e648e5 100644
--- a/lib/active_model_serializers/key_transform.rb
+++ b/lib/active_model_serializers/key_transform.rb
@@ -11,6 +11,7 @@ module ActiveModelSerializers
     # @see {https://github.com/rails/rails/blob/master/activesupport/lib/active_support/inflector/methods.rb#L66-L76 ActiveSupport::Inflector.camelize}
     def camel(value)
       case value
+      when Array then value.map { |item| camel(item) }
       when Hash then value.deep_transform_keys! { |key| camel(key) }
       when Symbol then camel(value.to_s).to_sym
       when String then value.underscore.camelize
@@ -25,6 +26,7 @@ module ActiveModelSerializers
     # @see {https://github.com/rails/rails/blob/master/activesupport/lib/active_support/inflector/methods.rb#L66-L76 ActiveSupport::Inflector.camelize}
     def camel_lower(value)
       case value
+      when Array then value.map { |item| camel_lower(item) }
       when Hash then value.deep_transform_keys! { |key| camel_lower(key) }
       when Symbol then camel_lower(value.to_s).to_sym
       when String then value.underscore.camelize(:lower)
@@ -40,6 +42,7 @@ module ActiveModelSerializers
     # @see {https://github.com/rails/rails/blob/master/activesupport/lib/active_support/inflector/methods.rb#L185-L187 ActiveSupport::Inflector.dasherize}
     def dash(value)
       case value
+      when Array then value.map { |item| dash(item) }
       when Hash then value.deep_transform_keys! { |key| dash(key) }
       when Symbol then dash(value.to_s).to_sym
       when String then value.underscore.dasherize
@@ -55,6 +58,7 @@ module ActiveModelSerializers
     # @see {https://github.com/rails/rails/blob/master/activesupport/lib/active_support/inflector/methods.rb#L89-L98 ActiveSupport::Inflector.underscore}
     def underscore(value)
       case value
+      when Array then value.map { |item| underscore(item) }
       when Hash then value.deep_transform_keys! { |key| underscore(key) }
       when Symbol then underscore(value.to_s).to_sym
       when String then value.underscore
diff --git a/test/active_model_serializers/key_transform_test.rb b/test/active_model_serializers/key_transform_test.rb
index c25f6ca4..b4ff4d31 100644
--- a/test/active_model_serializers/key_transform_test.rb
+++ b/test/active_model_serializers/key_transform_test.rb
@@ -60,6 +60,14 @@ module ActiveModelSerializers
         {
           value: nil,
           expected: nil
+        },
+        {
+          value: [
+            { some_value: 'value' }
+          ],
+          expected: [
+            { SomeValue: 'value' }
+          ]
         }
       ]
       scenarios.each do |s|
@@ -126,6 +134,14 @@ module ActiveModelSerializers
         {
           value: nil,
           expected: nil
+        },
+        {
+          value: [
+            { some_value: 'value' }
+          ],
+          expected: [
+            { someValue: 'value' }
+          ]
         }
       ]
       scenarios.each do |s|
@@ -188,6 +204,14 @@ module ActiveModelSerializers
         {
           value: nil,
           expected: nil
+        },
+        {
+          value: [
+            { 'some_value' => 'value' }
+          ],
+          expected: [
+            { 'some-value' => 'value' }
+          ]
         }
       ]
       scenarios.each do |s|
@@ -254,6 +278,14 @@ module ActiveModelSerializers
         {
           value: nil,
           expected: nil
+        },
+        {
+          value: [
+            { 'some-value' => 'value' }
+          ],
+          expected: [
+            { 'some_value' => 'value' }
+          ]
         }
       ]
       scenarios.each do |s|
diff --git a/test/adapter/attributes_test.rb b/test/adapter/attributes_test.rb
new file mode 100644
index 00000000..dee0c775
--- /dev/null
+++ b/test/adapter/attributes_test.rb
@@ -0,0 +1,43 @@
+require 'test_helper'
+
+module ActiveModelSerializers
+  module Adapter
+    class AttributesTest < ActiveSupport::TestCase
+      class Person
+        include ActiveModel::Model
+        include ActiveModel::Serialization
+
+        attr_accessor :first_name, :last_name
+      end
+
+      class PersonSerializer < ActiveModel::Serializer
+        attributes :first_name, :last_name
+      end
+
+      def setup
+        ActionController::Base.cache_store.clear
+      end
+
+      def test_serializable_hash
+        person = Person.new(first_name: 'Arthur', last_name: 'Dent')
+        serializer = PersonSerializer.new(person)
+        adapter = ActiveModelSerializers::Adapter::Attributes.new(serializer)
+
+        assert_equal({ first_name: 'Arthur', last_name: 'Dent' },
+          adapter.serializable_hash)
+      end
+
+      def test_serializable_hash_with_transform_key_casing
+        person = Person.new(first_name: 'Arthur', last_name: 'Dent')
+        serializer = PersonSerializer.new(person)
+        adapter = ActiveModelSerializers::Adapter::Attributes.new(
+          serializer,
+          key_transform: :camel_lower
+        )
+
+        assert_equal({ firstName: 'Arthur', lastName: 'Dent' },
+          adapter.serializable_hash)
+      end
+    end
+  end
+end