diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2218935..791bb91 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -34,6 +34,7 @@
   * `QueryMethodBefore32`: detect Path Item `query` usage in pre-3.2 documents (3.2 addition)
   * `AdditionalOperationsBefore32`: detect Path Item `additionalOperations` usage in pre-3.2 documents (3.2 addition)
   * `QuerystringBefore32`: detect Parameter `in: querystring` usage in pre-3.2 documents (3.2 addition; not validated at runtime)
+  * `CookieStyleBefore32`: detect Parameter `style: cookie` usage in pre-3.2 documents (3.2 addition)
 * expose the declared version as `OpenAPI#openapi_version` (a `Gem::Version`, or nil when the field is missing or malformed) so `SpecValidator` rules compare version ranges; a 3.2 document is checked by the 3.1-or-later rules
 * support 3.1-style numeric `exclusiveMinimum` / `exclusiveMaximum` in value validation (standalone bound, not a Boolean modifier on `minimum` / `maximum`)
 * support `type: "null"` (3.1 primitive) in value validation
diff --git a/lib/openapi_parser/spec_validator.rb b/lib/openapi_parser/spec_validator.rb
index 7216de5..e728c5a 100644
--- a/lib/openapi_parser/spec_validator.rb
+++ b/lib/openapi_parser/spec_validator.rb
@@ -30,6 +30,7 @@
 require_relative 'spec_validator/rules/query_method_before_32'
 require_relative 'spec_validator/rules/additional_operations_before_32'
 require_relative 'spec_validator/rules/querystring_before_32'
+require_relative 'spec_validator/rules/cookie_style_before_32'
 
 module OpenAPIParser
   class SpecViolationError < OpenAPIError
@@ -107,6 +108,7 @@ def rules
           Rules::QueryMethodBefore32,
           Rules::AdditionalOperationsBefore32,
           Rules::QuerystringBefore32,
+          Rules::CookieStyleBefore32,
         ]
       end
   end
diff --git a/lib/openapi_parser/spec_validator/rules/cookie_style_before_32.rb b/lib/openapi_parser/spec_validator/rules/cookie_style_before_32.rb
new file mode 100644
index 0000000..ed24207
--- /dev/null
+++ b/lib/openapi_parser/spec_validator/rules/cookie_style_before_32.rb
@@ -0,0 +1,26 @@
+module OpenAPIParser
+  class SpecValidator
+    module Rules
+      # `style: cookie` is a 3.2 Parameter style for cookie serialization.
+      # Runtime validation ignores `style`; this rule reports the version
+      # mismatch.
+      class CookieStyleBefore32 < Rule
+        def check(root)
+          return [] unless version_before?('3.2')
+
+          violations = []
+          each_node(root, OpenAPIParser::Schemas::Parameter) do |node|
+            raw = node.raw_schema
+            next unless raw.is_a?(Hash) && raw['style'] == 'cookie'
+
+            violations << violation(
+              path: "#{node.object_reference}/style",
+              message: '`style: cookie` is a 3.2 Parameter style; earlier documents have no such style',
+            )
+          end
+          violations
+        end
+      end
+    end
+  end
+end
diff --git a/sig/openapi_parser/spec_validator.rbs b/sig/openapi_parser/spec_validator.rbs
index 5c4e2cb..481c420 100644
--- a/sig/openapi_parser/spec_validator.rbs
+++ b/sig/openapi_parser/spec_validator.rbs
@@ -167,6 +167,10 @@ module OpenAPIParser
       class QuerystringBefore32 < Rule
         def check: (OpenAPIParser::Schemas::OpenAPI root) -> Array[SpecValidator::SpecViolation]
       end
+
+      class CookieStyleBefore32 < Rule
+        def check: (OpenAPIParser::Schemas::OpenAPI root) -> Array[SpecValidator::SpecViolation]
+      end
     end
   end
 
diff --git a/spec/data/openapi_3_2/cookie_style_31.yaml b/spec/data/openapi_3_2/cookie_style_31.yaml
new file mode 100644
index 0000000..2f943b3
--- /dev/null
+++ b/spec/data/openapi_3_2/cookie_style_31.yaml
@@ -0,0 +1,19 @@
+openapi: 3.1.0
+info:
+  title: Pet API
+  version: '1.0'
+paths:
+  /pets:
+    get:
+      summary: List pets
+      parameters:
+        # `style: cookie` is a 3.2 Parameter style; a 3.1 document has no
+        # such style, so its use here is a spec violation.
+        - name: session
+          in: cookie
+          style: cookie
+          schema:
+            type: string
+      responses:
+        '200':
+          description: OK
diff --git a/spec/data/openapi_3_2/cookie_style_32.yaml b/spec/data/openapi_3_2/cookie_style_32.yaml
new file mode 100644
index 0000000..baee688
--- /dev/null
+++ b/spec/data/openapi_3_2/cookie_style_32.yaml
@@ -0,0 +1,17 @@
+openapi: 3.2.0
+info:
+  title: Pet API
+  version: '1.0'
+paths:
+  /pets:
+    get:
+      summary: List pets
+      parameters:
+        - name: session
+          in: cookie
+          style: cookie
+          schema:
+            type: string
+      responses:
+        '200':
+          description: OK
diff --git a/spec/openapi_parser/spec_validator/integration_3_2_spec.rb b/spec/openapi_parser/spec_validator/integration_3_2_spec.rb
index 0bf5622..13c61c7 100644
--- a/spec/openapi_parser/spec_validator/integration_3_2_spec.rb
+++ b/spec/openapi_parser/spec_validator/integration_3_2_spec.rb
@@ -220,4 +220,18 @@ def expect_clean(file)
       expect_clean('querystring_32.yaml')
     end
   end
+
+  describe 'Parameter style: cookie (3.2 addition)' do
+    it 'warns on the version-mismatched document under :warn' do
+      expect_mismatch_warns('cookie_style_31.yaml', [:cookie_style_before32])
+    end
+
+    it 'raises SpecViolationError on the version-mismatched document under :raise' do
+      expect_mismatch_raises('cookie_style_31.yaml', [:cookie_style_before32])
+    end
+
+    it 'stays clean on the correctly-versioned document' do
+      expect_clean('cookie_style_32.yaml')
+    end
+  end
 end
diff --git a/spec/openapi_parser/spec_validator/rules/cookie_style_before_32_spec.rb b/spec/openapi_parser/spec_validator/rules/cookie_style_before_32_spec.rb
new file mode 100644
index 0000000..51461ff
--- /dev/null
+++ b/spec/openapi_parser/spec_validator/rules/cookie_style_before_32_spec.rb
@@ -0,0 +1,69 @@
+require_relative '../../../spec_helper'
+
+RSpec.describe 'OpenAPIParser::SpecValidator::Rules::CookieStyleBefore32' do
+  def base_doc(openapi_version_string, param)
+    {
+      'openapi' => openapi_version_string,
+      'info' => { 'title' => 'test', 'version' => '1.0' },
+      'paths' => {
+        '/pets' => {
+          'get' => {
+            'parameters' => [param],
+            'responses' => { '200' => { 'description' => 'OK' } },
+          },
+        },
+      },
+    }
+  end
+
+  def doc_with(openapi_version_string)
+    OpenAPIParser.parse(base_doc(openapi_version_string, { 'name' => 'session', 'in' => 'cookie', 'style' => 'cookie', 'schema' => { 'type' => 'string' } }), strict_reference_validation: false)
+  end
+
+  def doc_without(openapi_version_string)
+    OpenAPIParser.parse(base_doc(openapi_version_string, { 'name' => 'session', 'in' => 'cookie', 'style' => 'form', 'schema' => { 'type' => 'string' } }), strict_reference_validation: false)
+  end
+
+  def run_rule_for(root)
+    OpenAPIParser::SpecValidator::Rules::CookieStyleBefore32.new(root.openapi_version).check(root)
+  end
+
+  context 'with a 3.2 document using style: cookie' do
+    it 'reports no violation' do
+      expect(run_rule_for(doc_with('3.2.0'))).to eq []
+    end
+  end
+
+  context 'with a 3.2 document without style: cookie' do
+    it 'reports no violation' do
+      expect(run_rule_for(doc_without('3.2.0'))).to eq []
+    end
+  end
+
+  context 'with a 3.1 document using style: cookie' do
+    it 'reports one violation pointing at the field' do
+      violations = run_rule_for(doc_with('3.1.0'))
+      expect(violations.size).to eq 1
+      expect(violations.first.path).to eq '#/paths/~1pets/get/parameters/0/style'
+      expect(violations.first.rule_name).to eq :cookie_style_before32
+    end
+  end
+
+  context 'with a 3.1 document without style: cookie' do
+    it 'reports no violation' do
+      expect(run_rule_for(doc_without('3.1.0'))).to eq []
+    end
+  end
+
+  context 'with a 3.0 document using style: cookie' do
+    it 'reports one violation' do
+      expect(run_rule_for(doc_with('3.0.0')).size).to eq 1
+    end
+  end
+
+  context 'with a document whose openapi field is not a version' do
+    it 'reports no violation (rule skipped)' do
+      expect(run_rule_for(doc_with('not-a-version'))).to eq []
+    end
+  end
+end