diff --git a/lib/ldclient-rb/ldclient.rb b/lib/ldclient-rb/ldclient.rb
index 36388536..bbe65e48 100644
--- a/lib/ldclient-rb/ldclient.rb
+++ b/lib/ldclient-rb/ldclient.rb
@@ -81,6 +81,10 @@ def initialize(sdk_key, config = Config.default, wait_for_sec = 5)
       # The pid of the process in which the fork warning was last logged, or nil.
       @fork_warned_pid = Concurrent::AtomicReference.new(nil)
 
+      # Each flag lets the matching cached-data warning log once per client.
+      @cached_data_evaluation_warned = Concurrent::AtomicBoolean.new(false)
+      @cached_data_all_flags_warned = Concurrent::AtomicBoolean.new(false)
+
       start_up(wait_for_sec)
     end
 
@@ -629,7 +633,9 @@ def all_flags_state(context, options={})
 
       unless initialized?
         if @data_system.store.initialized?
-            @config.logger.warn { "Called all_flags_state before client initialization; using last known values from data store" }
+          if @cached_data_all_flags_warned.make_true
+            @config.logger.warn { "Called all_flags_state before client initialization; using last known values from data store. This message is logged once." }
+          end
         else
             @config.logger.warn { "Called all_flags_state before client initialization. Data store not available; returning empty state" }
             return FeatureFlagsState.new(false)
@@ -765,7 +771,9 @@ def flag_tracker
 
       if @data_system.data_availability != Impl::DataSystem::DataAvailability::REFRESHED
         if @data_system.data_availability == Impl::DataSystem::DataAvailability::CACHED
-          @config.logger.warn { "[LDClient] Client has not finished initializing; using last known values from feature store" }
+          if @cached_data_evaluation_warned.make_true
+            @config.logger.warn { "[LDClient] Client has not finished initializing; using last known values from feature store. This message is logged once." }
+          end
         else
           @config.logger.error { "[LDClient] Client has not finished initializing; feature store unavailable, returning default value" }
           detail = Evaluator.error_result(EvaluationReason::ERROR_CLIENT_NOT_READY, default)
diff --git a/spec/ldclient_cached_data_warning_spec.rb b/spec/ldclient_cached_data_warning_spec.rb
new file mode 100644
index 00000000..de0c983b
--- /dev/null
+++ b/spec/ldclient_cached_data_warning_spec.rb
@@ -0,0 +1,82 @@
+require "capturing_logger"
+require "mock_components"
+require "spec_helper"
+
+module LaunchDarkly
+  describe "LDClient cached-data warnings" do
+    let(:logger) { CapturingLogger.new }
+    let(:context) { basic_context }
+
+    # A data source that starts but never reports initialized. With a store that already holds
+    # data, the client evaluates with cached data.
+    def uninitialized_source
+      wait = double
+      allow(wait).to receive(:wait)
+      source = double
+      allow(source).to receive(:start).and_return(wait)
+      allow(source).to receive(:stop)
+      allow(source).to receive(:initialized?).and_return(false)
+      source
+    end
+
+    def initialized_store
+      store = InMemoryFeatureStore.new
+      store.init({ Impl::DataStore::FEATURES => {}, Impl::DataStore::SEGMENTS => {} })
+      store
+    end
+
+    def cached_data_config
+      test_config(logger: logger, feature_store: initialized_store, data_source: uninitialized_source)
+    end
+
+    def evaluation_warnings(logger)
+      logger.output.lines.grep(/Client has not finished initializing; using last known values/)
+    end
+
+    def all_flags_state_warnings(logger)
+      logger.output.lines.grep(/Called all_flags_state before client initialization; using last known values/)
+    end
+
+    it "logs the evaluation warning once per client" do
+      with_client(cached_data_config) do |client|
+        client.variation("flag", context, false)
+        client.variation("flag", context, false)
+        client.variation_detail("flag", context, false)
+        expect(evaluation_warnings(logger).length).to eq(1)
+      end
+    end
+
+    # all_flags_state checks LDClient#initialized?, which is true when the store holds data. The
+    # stub makes the client report not initialized so the cached-data branch runs.
+    it "logs the all_flags_state warning once per client" do
+      with_client(cached_data_config) do |client|
+        allow(client).to receive(:initialized?).and_return(false)
+        client.all_flags_state(context)
+        client.all_flags_state(context)
+        expect(all_flags_state_warnings(logger).length).to eq(1)
+      end
+    end
+
+    it "logs the evaluation and all_flags_state warnings independently" do
+      with_client(cached_data_config) do |client|
+        allow(client).to receive(:initialized?).and_return(false)
+        client.variation("flag", context, false)
+        client.all_flags_state(context)
+        client.variation("flag", context, false)
+        client.all_flags_state(context)
+        expect(evaluation_warnings(logger).length).to eq(1)
+        expect(all_flags_state_warnings(logger).length).to eq(1)
+      end
+    end
+
+    it "logs the warning again for a new client" do
+      with_client(cached_data_config) do |client|
+        client.variation("flag", context, false)
+      end
+      with_client(cached_data_config) do |client|
+        client.variation("flag", context, false)
+      end
+      expect(evaluation_warnings(logger).length).to eq(2)
+    end
+  end
+end