diff --git a/app/src/main/kotlin/com/google/samples/apps/nowinandroid/MainActivity.kt b/app/src/main/kotlin/com/google/samples/apps/nowinandroid/MainActivity.kt
index ecc23d80e0..461298550a 100644
--- a/app/src/main/kotlin/com/google/samples/apps/nowinandroid/MainActivity.kt
+++ b/app/src/main/kotlin/com/google/samples/apps/nowinandroid/MainActivity.kt
@@ -22,6 +22,7 @@ import androidx.activity.SystemBarStyle
 import androidx.activity.compose.setContent
 import androidx.activity.enableEdgeToEdge
 import androidx.activity.viewModels
+import androidx.appcompat.app.AppCompatDelegate
 import androidx.compose.runtime.CompositionLocalProvider
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
@@ -34,6 +35,7 @@ import androidx.lifecycle.repeatOnLifecycle
 import androidx.metrics.performance.JankStats
 import androidx.tracing.trace
 import com.google.samples.apps.nowinandroid.MainActivityUiState.Loading
+import com.google.samples.apps.nowinandroid.MainActivityUiState.Success
 import com.google.samples.apps.nowinandroid.core.analytics.AnalyticsHelper
 import com.google.samples.apps.nowinandroid.core.analytics.LocalAnalyticsHelper
 import com.google.samples.apps.nowinandroid.core.data.repository.UserNewsResourceRepository
@@ -41,12 +43,14 @@ import com.google.samples.apps.nowinandroid.core.data.util.NetworkMonitor
 import com.google.samples.apps.nowinandroid.core.data.util.TimeZoneMonitor
 import com.google.samples.apps.nowinandroid.core.designsystem.theme.NiaTheme
 import com.google.samples.apps.nowinandroid.core.ui.LocalTimeZone
+import com.google.samples.apps.nowinandroid.core.ui.toNightMode
 import com.google.samples.apps.nowinandroid.ui.NiaApp
 import com.google.samples.apps.nowinandroid.ui.rememberNiaAppState
 import com.google.samples.apps.nowinandroid.util.isSystemInDarkTheme
 import dagger.hilt.android.AndroidEntryPoint
 import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.distinctUntilChanged
+import kotlinx.coroutines.flow.filterIsInstance
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.onEach
 import kotlinx.coroutines.launch
@@ -79,6 +83,18 @@ class MainActivity : ComponentActivity() {
         val splashScreen = installSplashScreen()
         super.onCreate(savedInstanceState)
 
+        // Apply the saved dark theme config at startup to ensure the splash screen
+        // uses the correct theme. This addresses issue #633.
+        lifecycleScope.launch {
+            viewModel.uiState
+                .filterIsInstance<Success>()
+                .map { it.userData.darkThemeConfig.toNightMode() }
+                .first()
+                .let { mode ->
+                    AppCompatDelegate.setDefaultNightMode(mode)
+                }
+        }
+
         // We keep this as a mutable state, so that we can track changes inside the composition.
         // This allows us to react to dark/light mode changes.
         var themeSettings by mutableStateOf(
diff --git a/core/ui/src/main/kotlin/com/google/samples/apps/nowinandroid/core/ui/DarkThemeConfigExt.kt b/core/ui/src/main/kotlin/com/google/samples/apps/nowinandroid/core/ui/DarkThemeConfigExt.kt
new file mode 100644
index 0000000000..1d7aa97f0c
--- /dev/null
+++ b/core/ui/src/main/kotlin/com/google/samples/apps/nowinandroid/core/ui/DarkThemeConfigExt.kt
@@ -0,0 +1,29 @@
+/*
+ * Copyright 2026 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.samples.apps.nowinandroid.core.ui
+
+import androidx.appcompat.app.AppCompatDelegate
+import com.google.samples.apps.nowinandroid.core.model.data.DarkThemeConfig
+
+/**
+ * Converts [DarkThemeConfig] to [AppCompatDelegate] night mode constant.
+ */
+fun DarkThemeConfig.toNightMode(): Int = when (this) {
+    DarkThemeConfig.FOLLOW_SYSTEM -> AppCompatDelegate.MODE_NIGHT_FOLLOW_SYSTEM
+    DarkThemeConfig.LIGHT -> AppCompatDelegate.MODE_NIGHT_NO
+    DarkThemeConfig.DARK -> AppCompatDelegate.MODE_NIGHT_YES
+}
diff --git a/feature/settings/impl/src/main/kotlin/com/google/samples/apps/nowinandroid/feature/settings/impl/SettingsViewModel.kt b/feature/settings/impl/src/main/kotlin/com/google/samples/apps/nowinandroid/feature/settings/impl/SettingsViewModel.kt
index 274f916d13..ff5f67c094 100644
--- a/feature/settings/impl/src/main/kotlin/com/google/samples/apps/nowinandroid/feature/settings/impl/SettingsViewModel.kt
+++ b/feature/settings/impl/src/main/kotlin/com/google/samples/apps/nowinandroid/feature/settings/impl/SettingsViewModel.kt
@@ -16,11 +16,13 @@
 
 package com.google.samples.apps.nowinandroid.feature.settings.impl
 
+import androidx.appcompat.app.AppCompatDelegate
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import com.google.samples.apps.nowinandroid.core.data.repository.UserDataRepository
 import com.google.samples.apps.nowinandroid.core.model.data.DarkThemeConfig
 import com.google.samples.apps.nowinandroid.core.model.data.ThemeBrand
+import com.google.samples.apps.nowinandroid.core.ui.toNightMode
 import com.google.samples.apps.nowinandroid.feature.settings.impl.SettingsUiState.Loading
 import com.google.samples.apps.nowinandroid.feature.settings.impl.SettingsUiState.Success
 import dagger.hilt.android.lifecycle.HiltViewModel
@@ -62,6 +64,11 @@ class SettingsViewModel @Inject constructor(
     fun updateDarkThemeConfig(darkThemeConfig: DarkThemeConfig) {
         viewModelScope.launch {
             userDataRepository.setDarkThemeConfig(darkThemeConfig)
+            
+            // Apply the night mode at the application level to ensure the splash screen
+            // uses the correct theme on cold start. This addresses issue #633.
+            // Reference: https://developer.android.com/develop/ui/views/theming/darktheme#change-themes
+            AppCompatDelegate.setDefaultNightMode(darkThemeConfig.toNightMode())
         }
     }