diff --git a/collector/internal/lifecycle/manager.go b/collector/internal/lifecycle/manager.go
index 02203e4941..5e99b7ff82 100644
--- a/collector/internal/lifecycle/manager.go
+++ b/collector/internal/lifecycle/manager.go
@@ -22,6 +22,7 @@ import (
 	"path/filepath"
 	"sync"
 	"syscall"
+	"time"
 
 	"github.com/open-telemetry/opentelemetry-lambda/collector/lambdalifecycle"
 
@@ -53,9 +54,10 @@ type manager struct {
 	wg                 sync.WaitGroup
 	lifecycleListeners []lambdalifecycle.Listener
 	initType           lambdalifecycle.InitType
+	startTime          time.Time
 }
 
-func NewManager(ctx context.Context, logger *zap.Logger, version string) (context.Context, *manager) {
+func NewManager(ctx context.Context, logger *zap.Logger, version string, startTime time.Time) (context.Context, *manager) {
 	ctx, cancel := context.WithCancel(ctx)
 
 	sigs := make(chan os.Signal, 1)
@@ -102,6 +104,7 @@ func NewManager(ctx context.Context, logger *zap.Logger, version string) (contex
 		extensionClient: extensionClient,
 		listener:        listener,
 		initType:        initType,
+		startTime:       startTime,
 	}
 
 	factories, _ := lambdacomponents.Components(res.ExtensionID)
@@ -119,6 +122,8 @@ func (lm *manager) Run(ctx context.Context) error {
 		return err
 	}
 
+	lm.logger.Info("OpenTelemetry Lambda extension startup complete", zap.Duration("startup_duration", time.Since(lm.startTime)))
+
 	lm.wg.Add(1)
 	go func() {
 		if err := lm.processEvents(ctx); err != nil {
diff --git a/collector/internal/lifecycle/manager_test.go b/collector/internal/lifecycle/manager_test.go
index b52effe8dc..fc407f187f 100644
--- a/collector/internal/lifecycle/manager_test.go
+++ b/collector/internal/lifecycle/manager_test.go
@@ -24,15 +24,101 @@ import (
 	"os"
 	"path/filepath"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"go.uber.org/zap"
 	"go.uber.org/zap/zaptest"
+	"go.uber.org/zap/zaptest/observer"
 
 	"github.com/open-telemetry/opentelemetry-lambda/collector/internal/extensionapi"
 	"github.com/open-telemetry/opentelemetry-lambda/collector/internal/telemetryapi"
 )
 
+const startupCompleteMsg = "OpenTelemetry Lambda extension startup complete"
+
+func TestRunLogsStartupDuration(t *testing.T) {
+	shutdownServer := func(t *testing.T) *httptest.Server {
+		server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			w.WriteHeader(200)
+			_, err := w.Write([]byte(`{"time":"2006-01-02T15:04:05.000Z", "eventType":"SHUTDOWN", "record":{}}`))
+			require.NoError(t, err)
+			_, err = io.ReadAll(r.Body)
+			require.NoError(t, err, "failed to read request body: %v", err)
+		}))
+		t.Cleanup(server.Close)
+		return server
+	}
+	extensionEventTypes := []extensionapi.EventType{extensionapi.Invoke, extensionapi.Shutdown}
+
+	t.Run("emits a single startup-complete log with a startup_duration field", func(t *testing.T) {
+		core, logs := observer.New(zap.InfoLevel)
+		logger := zap.New(core)
+
+		server := shutdownServer(t)
+		u, err := url.Parse(server.URL)
+		require.NoError(t, err)
+
+		lm := manager{
+			collector:       &MockCollector{},
+			logger:          logger,
+			listener:        telemetryapi.NewListener(logger),
+			extensionClient: extensionapi.NewClient(logger, u.Host, extensionEventTypes),
+			startTime:       time.Now(),
+		}
+		require.NoError(t, lm.Run(context.Background()))
+
+		entries := logs.FilterMessage(startupCompleteMsg).All()
+		require.Len(t, entries, 1, "expected exactly one startup-complete log")
+		field, ok := entries[0].ContextMap()["startup_duration"]
+		require.True(t, ok, "startup-complete log must carry a startup_duration field")
+		duration, ok := field.(time.Duration)
+		require.True(t, ok, "startup_duration must be a duration field")
+		assert.GreaterOrEqual(t, duration, time.Duration(0), "startup_duration must be non-negative")
+	})
+
+	t.Run("zero-value start time produces a valid duration without panicking", func(t *testing.T) {
+		core, logs := observer.New(zap.InfoLevel)
+		logger := zap.New(core)
+
+		server := shutdownServer(t)
+		u, err := url.Parse(server.URL)
+		require.NoError(t, err)
+
+		lm := manager{
+			collector:       &MockCollector{},
+			logger:          logger,
+			listener:        telemetryapi.NewListener(logger),
+			extensionClient: extensionapi.NewClient(logger, u.Host, extensionEventTypes),
+			// startTime intentionally left as the zero value.
+		}
+		require.NotPanics(t, func() {
+			require.NoError(t, lm.Run(context.Background()))
+		})
+
+		entries := logs.FilterMessage(startupCompleteMsg).All()
+		require.Len(t, entries, 1)
+		duration, ok := entries[0].ContextMap()["startup_duration"].(time.Duration)
+		require.True(t, ok)
+		assert.GreaterOrEqual(t, duration, time.Duration(0))
+	})
+
+	t.Run("does not emit startup-complete log when collector start fails", func(t *testing.T) {
+		core, logs := observer.New(zap.InfoLevel)
+		logger := zap.New(core)
+
+		lm := manager{
+			collector:       &MockCollector{err: fmt.Errorf("test start error")},
+			logger:          logger,
+			extensionClient: extensionapi.NewClient(logger, "", extensionEventTypes),
+			startTime:       time.Now(),
+		}
+		require.Error(t, lm.Run(context.Background()))
+		assert.Equal(t, 0, logs.FilterMessage(startupCompleteMsg).Len(), "no startup-complete log on failure")
+	})
+}
+
 type MockCollector struct {
 	err error
 }
diff --git a/collector/main.go b/collector/main.go
index 4304997e88..c4430f45f2 100644
--- a/collector/main.go
+++ b/collector/main.go
@@ -18,6 +18,7 @@ import (
 	"context"
 	"flag"
 	"fmt"
+	"time"
 
 	"github.com/open-telemetry/opentelemetry-lambda/collector/lambdalifecycle"
 
@@ -44,9 +45,10 @@ func main() {
 	}
 
 	logger := logging.NewLogger()
+	startTime := time.Now()
 	logger.Info("Launching OpenTelemetry Lambda extension", zap.String("version", Version))
 
-	ctx, lm := lifecycle.NewManager(context.Background(), logger, Version)
+	ctx, lm := lifecycle.NewManager(context.Background(), logger, Version, startTime)
 
 	// Set the new lifecycle manager as the lifecycle notifier for all other components.
 	lambdalifecycle.SetNotifier(lm)