diff --git a/lib/ldclient-rb/config.rb b/lib/ldclient-rb/config.rb
index 1b77ac16..bc116471 100644
--- a/lib/ldclient-rb/config.rb
+++ b/lib/ldclient-rb/config.rb
@@ -34,7 +34,7 @@ class Config
     # @option opts [Float] :poll_interval (30) See {#poll_interval}.
     # @option opts [Boolean] :stream (true) See {#stream?}.
     # @option opts [Boolean] all_attributes_private (false) See {#all_attributes_private}.
-    # @option opts [Array] :private_attributes See {#private_attributes}.
+    # @option opts [Enumerable<String>] :private_attributes See {#private_attributes}.
     # @option opts [Boolean] :send_events (true) See {#send_events}.
     # @option opts [Integer] :context_keys_capacity (1000) See {#context_keys_capacity}.
     # @option opts [Float] :context_keys_flush_interval (300) See {#context_keys_flush_interval}.
@@ -69,7 +69,7 @@ def initialize(opts = {})
       @offline = opts.has_key?(:offline) ? opts[:offline] : Config.default_offline
       @poll_interval = opts.has_key?(:poll_interval) && opts[:poll_interval] > Config.default_poll_interval ? opts[:poll_interval] : Config.default_poll_interval
       @all_attributes_private = opts[:all_attributes_private] || false
-      @private_attributes = opts[:private_attributes] || []
+      @private_attributes = Set.new(opts[:private_attributes] || []).freeze
       @send_events = opts.has_key?(:send_events) ? opts[:send_events] : Config.default_send_events
       @compress_events = opts.has_key?(:compress_events) ? opts[:compress_events] : Config.default_compress_events
       @context_keys_capacity = opts[:context_keys_capacity] || Config.default_context_keys_capacity
@@ -255,7 +255,7 @@ def offline?
     attr_reader :all_attributes_private
 
     #
-    # A list of context attribute names that should always be considered private. This means that the
+    # A set of context attribute names that should always be considered private. This means that the
     # attribute values will not be sent to LaunchDarkly in analytics events and will not appear on
     # the LaunchDarkly dashboard.
     #
@@ -268,7 +268,7 @@ def offline?
     #
     # @see https://docs.launchdarkly.com/sdk/features/user-context-config#using-private-attributes
     #
-    # @return [Array<String>]
+    # @return [Set<String>]
     # @see #all_attributes_private
     #
     attr_reader :private_attributes
diff --git a/lib/ldclient-rb/context.rb b/lib/ldclient-rb/context.rb
index 58e8c40a..616e4512 100644
--- a/lib/ldclient-rb/context.rb
+++ b/lib/ldclient-rb/context.rb
@@ -44,7 +44,7 @@ class LDContext
     private_constant :ERR_KIND_MULTI_DUPLICATES
     ERR_CUSTOM_NON_HASH = 'context custom must be a hash'
     private_constant :ERR_CUSTOM_NON_HASH
-    ERR_PRIVATE_NON_ARRAY = 'context private attributes must be an array'
+    ERR_PRIVATE_NON_ARRAY = 'context private attributes must be an array or a set'
 
     # @return [String, nil] Returns the key for this context
     attr_reader :key
@@ -66,7 +66,7 @@ class LDContext
     # @param name [String, nil]
     # @param anonymous [Boolean, nil]
     # @param attributes [Hash, nil]
-    # @param private_attributes [Array<String>, nil]
+    # @param private_attributes [Array<String>, Set<String>, nil]
     # @param error [String, nil]
     # @param contexts [Array<LDContext>, nil]
     #
@@ -82,6 +82,7 @@ def initialize(key, fully_qualified_key, kind, name = nil, anonymous = nil, attr
         reference = Reference.create(attribute)
         @private_attributes.add(reference) if reference.error.nil?
       end
+      @private_attributes.freeze
       @error = error
       @contexts = contexts
       @is_multi = !contexts.nil?
@@ -91,12 +92,9 @@ def initialize(key, fully_qualified_key, kind, name = nil, anonymous = nil, attr
     protected attr_reader :name, :anonymous, :attributes
 
     #
-    # @return [Array<Reference>] Returns the private attributes associated with this LDContext
+    # @return [Set<Reference>] Returns the private attributes associated with this LDContext. The set is frozen.
     #
-    def private_attributes
-      # TODO(sc-227265): Return a set instead of an array.
-      @private_attributes.to_a
-    end
+    attr_reader :private_attributes
 
     #
     # @return [Boolean] Is this LDContext a multi-kind context?
@@ -353,8 +351,7 @@ def ==(other)
       return false unless self.anonymous == other.anonymous
       return false unless self.attributes == other.attributes
 
-      # TODO(sc-227265): Calling .to_set is unnecessary once private_attributes are sets.
-      return false unless self.private_attributes.to_set == other.private_attributes.to_set
+      return false unless self.private_attributes == other.private_attributes
 
       true
     end
@@ -413,7 +410,7 @@ def to_h
 
       hash[:name] = name unless name.nil?
       hash[:anonymous] = anonymous if anonymous
-      hash[:_meta] = {privateAttributes: private_attributes} unless private_attributes.empty?
+      hash[:_meta] = {privateAttributes: private_attributes.to_a} unless private_attributes.empty?
 
       hash
     end
@@ -570,7 +567,7 @@ def self.create_multi(contexts)
 
       meta = data.fetch(:_meta, {})
       private_attributes = meta[:privateAttributes]
-      if private_attributes && !private_attributes.is_a?(Array)
+      if private_attributes && !private_attributes.is_a?(Array) && !private_attributes.is_a?(Set)
         return create_invalid_context(ERR_PRIVATE_NON_ARRAY)
       end
 
diff --git a/lib/ldclient-rb/impl/context_filter.rb b/lib/ldclient-rb/impl/context_filter.rb
index 30c6ecdb..736611f0 100644
--- a/lib/ldclient-rb/impl/context_filter.rb
+++ b/lib/ldclient-rb/impl/context_filter.rb
@@ -5,7 +5,7 @@ module Impl
     class ContextFilter
       #
       # @param all_attributes_private [Boolean]
-      # @param private_attributes [Array<String>]
+      # @param private_attributes [Enumerable<String>]
       # @param logger [Logger, nil]
       #
       def initialize(all_attributes_private, private_attributes, logger = nil)
@@ -13,7 +13,7 @@ def initialize(all_attributes_private, private_attributes, logger = nil)
         @logger = logger
         @non_symbol_name_logged = Concurrent::AtomicBoolean.new(false)
 
-        @private_attributes = []
+        @private_attributes = Set.new
         private_attributes.each do |attribute|
           reference = LaunchDarkly::Reference.create(attribute)
           @private_attributes << reference if reference.error.nil?
@@ -75,7 +75,7 @@ def filter_redact_anonymous(context)
         filtered[:anonymous] = true if anonymous
 
         redacted = []
-        private_attributes = @private_attributes + context.private_attributes
+        private_attributes = @private_attributes | context.private_attributes
 
         name = context.get_value(:name)
         if !name.nil? && !check_whole_attribute_private(Reference.create_literal(:name), private_attributes, redacted, anonymous && redact_anonymous)
@@ -103,7 +103,7 @@ def filter_redact_anonymous(context)
       # Check if an entire attribute should be redacted.
       #
       # @param attribute [Reference]
-      # @param private_attributes [Array<Reference>]
+      # @param private_attributes [Set<Reference>]
       # @param redacted [Array<Symbol>]
       # @param redact_all [Boolean]
       # @return [Boolean]
@@ -130,7 +130,7 @@ def filter_redact_anonymous(context)
       # @param parent_path [Array<String>, nil]
       # @param name [String]
       # @param value [any]
-      # @param private_attributes [Array<Reference>]
+      # @param private_attributes [Set<Reference>]
       # @param redacted [Array<Symbol>]
       # @param visited [Array<Hash>]
       # @return [any]
diff --git a/lib/ldclient-rb/reference.rb b/lib/ldclient-rb/reference.rb
index d50b1e6d..3c93bdaf 100644
--- a/lib/ldclient-rb/reference.rb
+++ b/lib/ldclient-rb/reference.rb
@@ -125,10 +125,14 @@ def initialize(raw_path, components = [], error = nil)
     # validation fails, {#error} will return a non-nil error and any SDK method
     # that takes this Reference as a parameter will consider it invalid.
     #
-    # @param value [String, Symbol]
+    # If the value is a Reference, this method returns the same Reference.
+    #
+    # @param value [String, Symbol, Reference]
     # @return [Reference]
     #
     def self.create(value)
+      return value if value.is_a?(Reference)
+
       unless value.is_a?(String) || value.is_a?(Symbol)
         return new(value, [], ERR_EMPTY)
       end
diff --git a/spec/config_spec.rb b/spec/config_spec.rb
index 687b9b09..eb11a3de 100644
--- a/spec/config_spec.rb
+++ b/spec/config_spec.rb
@@ -135,5 +135,16 @@ module LaunchDarkly
         expect(subject.new(omit_anonymous_contexts: true).omit_anonymous_contexts).to eq true
       end
     end
+    describe ".private_attributes" do
+      it "defaults to an empty set" do
+        expect(subject.new.private_attributes).to eq Set.new
+      end
+      it "converts an array to a set" do
+        expect(subject.new(private_attributes: ["name", "email", "name"]).private_attributes).to eq Set["name", "email"]
+      end
+      it "is frozen" do
+        expect(subject.new(private_attributes: ["name"]).private_attributes).to be_frozen
+      end
+    end
   end
 end
diff --git a/spec/context_spec.rb b/spec/context_spec.rb
index 44be8e4a..f4a65006 100644
--- a/spec/context_spec.rb
+++ b/spec/context_spec.rb
@@ -77,6 +77,19 @@ module LaunchDarkly
           expect(subject.create(context).valid?).to be false
         end
 
+        it "accepts privateAttributes as a set" do
+          context = subject.create({ key: "user-key", kind: "user", _meta: { privateAttributes: Set["email"] } })
+          expect(context.valid?).to be true
+          expect(context.private_attributes).to eq(Set[LaunchDarkly::Reference.create("email")])
+        end
+
+        it "accepts privateAttributes from another context" do
+          original = subject.create({ key: "user-key", kind: "user", _meta: { privateAttributes: ["email", "/address/city"] } })
+          context = subject.create({ key: "user-key", kind: "user", _meta: { privateAttributes: original.private_attributes } })
+          expect(context.valid?).to be true
+          expect(context.private_attributes).to eq(original.private_attributes)
+        end
+
         it "creates the correct fully qualified key" do
           expect(subject.create({ key: "user-key", kind: "user" }).fully_qualified_key).to eq("user-key")
           expect(subject.create({ key: "org-key", kind: "org" }).fully_qualified_key).to eq("org:org-key")
@@ -394,6 +407,19 @@ module LaunchDarkly
       end
     end
 
+    describe "private attributes" do
+      it "returns a frozen set of references" do
+        context = subject.create({ key: 'context-key', kind: 'user', _meta: { privateAttributes: ['name', 'address/city', 'name'] } })
+        expect(context.private_attributes).to be_a(Set)
+        expect(context.private_attributes).to be_frozen
+        expect(context.private_attributes).to eq(Set[LaunchDarkly::Reference.create('name'), LaunchDarkly::Reference.create('address/city')])
+      end
+
+      it "returns an empty set when none are given" do
+        expect(subject.create({ key: 'context-key', kind: 'user' }).private_attributes).to eq(Set.new)
+      end
+    end
+
     describe "equality comparisons" do
       it "wrong types are not equal" do
         context = subject.create({ key: 'context-key', kind: 'user' })
diff --git a/spec/reference_spec.rb b/spec/reference_spec.rb
index 4c0d0a51..a4a661f7 100644
--- a/spec/reference_spec.rb
+++ b/spec/reference_spec.rb
@@ -90,6 +90,11 @@ module LaunchDarkly
       end
     end
 
+    it "returns the same reference when given a reference" do
+      reference = Reference.create("/a/b")
+      expect(Reference.create(reference)).to be(reference)
+    end
+
     describe "creating literal references" do
       it "can create valid references" do
         [