diff --git a/aws-sdk-core/lib/aws-sdk-core/dynamodb/attribute_value.rb b/aws-sdk-core/lib/aws-sdk-core/dynamodb/attribute_value.rb
index 9770496a086..b42ee78bc06 100644
--- a/aws-sdk-core/lib/aws-sdk-core/dynamodb/attribute_value.rb
+++ b/aws-sdk-core/lib/aws-sdk-core/dynamodb/attribute_value.rb
@@ -33,6 +33,7 @@ def format(obj)
               list[:l] << format(value)
             end
           when String then { s: obj }
+          when Symbol then { s: obj.to_s }
           when Numeric then { n: obj.to_s }
           when StringIO, IO then { b: obj }
           when Set then format_set(obj)
@@ -49,7 +50,7 @@ def format(obj)
 
         def format_set(set)
           case set.first
-          when String then { ss: set.map(&:to_s) }
+          when String, Symbol then { ss: set.map(&:to_s) }
           when Numeric then { ns: set.map(&:to_s) }
           when StringIO, IO then { bs: set.to_a }
           else
diff --git a/aws-sdk-core/spec/aws/dynamodb/attribute_value_spec.rb b/aws-sdk-core/spec/aws/dynamodb/attribute_value_spec.rb
index cb9384b0794..0e4929ef921 100644
--- a/aws-sdk-core/spec/aws/dynamodb/attribute_value_spec.rb
+++ b/aws-sdk-core/spec/aws/dynamodb/attribute_value_spec.rb
@@ -37,6 +37,11 @@ module DynamoDB
           expect(formatted).to eq(ss: %w(abc mno))
         end
 
+        it 'converts symbol sets to :ss (string set)' do
+          formatted = value.marshal(Set.new([:abc, :mno]))
+          expect(formatted).to eq(ss: %w(abc mno))
+        end
+
         it 'converts numeric sets to :ns (number set)' do
           formatted = value.marshal(Set.new([123, 456]))
           expect(formatted).to eq(ns: %w(123 456))
@@ -59,6 +64,10 @@ module DynamoDB
           expect(value.marshal('abc')).to eq(s: 'abc')
         end
 
+        it 'converts symbol to :s' do
+          expect(value.marshal(:abc)).to eq(s: 'abc')
+        end
+
         it 'converts booleans :bool' do
           # supports both true and false
           expect(value.marshal(true)).to eq(bool: true)