diff --git a/res/values/strings.xml b/res/values/strings.xml
index c891432025d..5b9fda01554 100644
--- a/res/values/strings.xml
+++ b/res/values/strings.xml
@@ -10456,6 +10456,30 @@
         <item quantity="other"><xliff:g id="count" example="2">%1$d</xliff:g> SIMs</item>
     </plurals>
 
+    <!-- Network & internet page. Summary indicating that a SIM is used by default for calls when
+         multiple SIMs are present. [CHAR LIMIT=40] -->
+    <string name="default_for_calls">Default for calls</string>
+    <!-- Network & internet page. Summary indicating that a SIM is used by default for SMS messages
+         when multiple SIMs are present. [CHAR LIMIT=40] -->
+    <string name="default_for_sms">Default for SMS</string>
+    <!-- Network & internet page. Summary indicating that a SIM is used by default for calls and SMS
+         messages when multiple SIMs are present. [CHAR LIMIT=40] -->
+    <string name="default_for_calls_and_sms">Default for calls &amp; SMS</string>
+    <!-- Network & internet page. Summary indicating that a SIM is used by default for mobile data
+         when multiple SIMs are present. [CHAR LIMIT=40] -->
+    <string name="default_for_mobile_data">Default for mobile data</string>
+    <!-- Network & internet page. Summary indicating that a SIM has an active mobile data connection
+         when multiple SIMs are present. [CHAR LIMIT=40] -->
+    <string name="mobile_data_active">Mobile data active</string>
+    <!-- Network & internet page. Summary indicating that a SIM is used by default for mobile data
+         when multiple SIMs are present, but mobile data is currently turned off.
+         [CHAR LIMIT=40] -->
+    <string name="mobile_data_off">Mobile data off</string>
+    <!-- Network & internet page. Summary indicating that a SIM is available to be used for services
+         such as calls, SMS, or data when multiple SIMs are present, but is not currently the
+          default SIM for any of those services. [CHAR LIMIT=40] -->
+    <string name="subscription_available">Available</string>
+
     <!-- Title of item shown at the bottom of the page listing multiple mobile service
          subscriptions; tapping it leads to a UI to add more [CHAR LIMIT=40] -->
     <string name="mobile_network_list_add_more">Add more</string>
diff --git a/src/com/android/settings/network/SubscriptionsPreferenceController.java b/src/com/android/settings/network/SubscriptionsPreferenceController.java
index 6952a1e9fbd..a6397827b32 100644
--- a/src/com/android/settings/network/SubscriptionsPreferenceController.java
+++ b/src/com/android/settings/network/SubscriptionsPreferenceController.java
@@ -24,6 +24,7 @@ import android.content.Intent;
 import android.provider.Settings;
 import android.telephony.SubscriptionInfo;
 import android.telephony.SubscriptionManager;
+import android.telephony.TelephonyManager;
 
 import androidx.collection.ArrayMap;
 import androidx.lifecycle.Lifecycle;
@@ -136,11 +137,10 @@ public class SubscriptionsPreferenceController extends AbstractPreferenceControl
                 mPreferenceGroup.addPreference(pref);
             }
             pref.setTitle(info.getDisplayName());
+            pref.setSummary(getSummary(subId));
             pref.setIcon(R.drawable.ic_network_cell);
             pref.setOrder(order++);
 
-            // TODO(asargent) - set summary here to indicate default for calls/sms and data
-
             pref.setOnPreferenceClickListener(clickedPref -> {
                 final Intent intent = new Intent(mContext, MobileNetworkActivity.class);
                 intent.putExtra(Settings.EXTRA_SUB_ID, subId);
@@ -158,6 +158,56 @@ public class SubscriptionsPreferenceController extends AbstractPreferenceControl
         mUpdateListener.onChildrenUpdated();
     }
 
+    /**
+     * The summary can have either 1 or 2 lines depending on which services (calls, SMS, data) this
+     * subscription is the default for.
+     *
+     * If this subscription is the default for calls and/or SMS, we add a line to show that.
+     *
+     * If this subscription is the default for data, we add a line with detail about
+     * whether the data connection is active.
+     *
+     * If a subscription isn't the default for anything, we just say it is available.
+     */
+    protected String getSummary(int subId) {
+        final int callsDefaultSubId = SubscriptionManager.getDefaultVoiceSubscriptionId();
+        final int smsDefaultSubId = SubscriptionManager.getDefaultSmsSubscriptionId();
+        final int dataDefaultSubId = SubscriptionManager.getDefaultDataSubscriptionId();
+
+        String line1 = null;
+        if (subId == callsDefaultSubId && subId == smsDefaultSubId) {
+            line1 = mContext.getString(R.string.default_for_calls_and_sms);
+        } else if (subId == callsDefaultSubId) {
+            line1 = mContext.getString(R.string.default_for_calls);
+        } else if (subId == smsDefaultSubId) {
+            line1 = mContext.getString(R.string.default_for_sms);
+        }
+
+        String line2 = null;
+        if (subId == dataDefaultSubId) {
+            final TelephonyManager telMgrForSub = mContext.getSystemService(
+                    TelephonyManager.class).createForSubscriptionId(subId);
+            final int dataState = telMgrForSub.getDataState();
+            if (dataState == TelephonyManager.DATA_CONNECTED) {
+                line2 = mContext.getString(R.string.mobile_data_active);
+            } else if (!telMgrForSub.isDataEnabled()) {
+                line2 = mContext.getString(R.string.mobile_data_off);
+            } else {
+                line2 = mContext.getString(R.string.default_for_mobile_data);
+            }
+        }
+
+        if (line1 != null && line2 != null) {
+            return String.join(System.lineSeparator(), line1, line2);
+        } else if (line1 != null) {
+            return line1;
+        } else if (line2 != null) {
+            return line2;
+        } else {
+            return mContext.getString(R.string.subscription_available);
+        }
+    }
+
     /**
      *
      * @return true if there are at least 2 available subscriptions.
diff --git a/tests/robotests/src/com/android/settings/network/SubscriptionsPreferenceControllerTest.java b/tests/robotests/src/com/android/settings/network/SubscriptionsPreferenceControllerTest.java
index 70536997493..a4847457441 100644
--- a/tests/robotests/src/com/android/settings/network/SubscriptionsPreferenceControllerTest.java
+++ b/tests/robotests/src/com/android/settings/network/SubscriptionsPreferenceControllerTest.java
@@ -20,6 +20,7 @@ import static android.telephony.SubscriptionManager.INVALID_SUBSCRIPTION_ID;
 
 import static com.google.common.truth.Truth.assertThat;
 
+import static org.mockito.ArgumentMatchers.anyInt;
 import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.doReturn;
 import static org.mockito.Mockito.mock;
@@ -34,7 +35,9 @@ import android.content.Intent;
 import android.provider.Settings;
 import android.telephony.SubscriptionInfo;
 import android.telephony.SubscriptionManager;
+import android.telephony.TelephonyManager;
 
+import com.android.settings.R;
 import com.android.settingslib.core.lifecycle.Lifecycle;
 
 import org.junit.After;
@@ -46,6 +49,8 @@ import org.mockito.Mock;
 import org.mockito.MockitoAnnotations;
 import org.robolectric.Robolectric;
 import org.robolectric.RobolectricTestRunner;
+import org.robolectric.annotation.Config;
+import org.robolectric.shadows.ShadowSubscriptionManager;
 
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -57,6 +62,7 @@ import androidx.preference.PreferenceCategory;
 import androidx.preference.PreferenceScreen;
 
 @RunWith(RobolectricTestRunner.class)
+@Config(shadows = ShadowSubscriptionManager.class)
 public class SubscriptionsPreferenceControllerTest {
     private static final String KEY = "preference_group";
 
@@ -66,6 +72,8 @@ public class SubscriptionsPreferenceControllerTest {
     private PreferenceCategory mPreferenceCategory;
     @Mock
     private SubscriptionManager mSubscriptionManager;
+    @Mock
+    private TelephonyManager mTelephonyManager;
 
     private Context mContext;
     private LifecycleOwner mLifecycleOwner;
@@ -81,6 +89,8 @@ public class SubscriptionsPreferenceControllerTest {
         mLifecycleOwner = () -> mLifecycle;
         mLifecycle = new Lifecycle(mLifecycleOwner);
         when(mContext.getSystemService(SubscriptionManager.class)).thenReturn(mSubscriptionManager);
+        when(mContext.getSystemService(TelephonyManager.class)).thenReturn(mTelephonyManager);
+        when(mTelephonyManager.createForSubscriptionId(anyInt())).thenReturn(mTelephonyManager);
         when(mScreen.findPreference(eq(KEY))).thenReturn(mPreferenceCategory);
         when(mPreferenceCategory.getContext()).thenReturn(mContext);
         mOnChildUpdatedCount = 0;
@@ -280,4 +290,69 @@ public class SubscriptionsPreferenceControllerTest {
     public void threePreferences_thirdPreferenceClicked_correctIntentFires() {
         runPreferenceClickTest(3, 2);
     }
+
+    @Test
+    public void getSummary_twoSubsOneDefaultForEverythingDataActive() {
+        final SubscriptionInfo sub1 = mock(SubscriptionInfo.class);
+        final SubscriptionInfo sub2 = mock(SubscriptionInfo.class);
+        when(sub1.getSubscriptionId()).thenReturn(11);
+        when(sub2.getSubscriptionId()).thenReturn(22);
+        SubscriptionUtil.setAvailableSubscriptionsForTesting(Arrays.asList(sub1, sub2));
+
+        ShadowSubscriptionManager.setDefaultDataSubscriptionId(11);
+        ShadowSubscriptionManager.setDefaultSmsSubscriptionId(11);
+        ShadowSubscriptionManager.setDefaultVoiceSubscriptionId(11);
+        when(mTelephonyManager.getDataState()).thenReturn(TelephonyManager.DATA_CONNECTED);
+
+        assertThat(mController.getSummary(11)).isEqualTo(
+                mContext.getString(R.string.default_for_calls_and_sms) + System.lineSeparator()
+                        + mContext.getString(R.string.mobile_data_active));
+
+        assertThat(mController.getSummary(22)).isEqualTo(
+                mContext.getString(R.string.subscription_available));
+    }
+
+    @Test
+    public void getSummary_twoSubsOneDefaultForEverythingDataDisabled() {
+        final SubscriptionInfo sub1 = mock(SubscriptionInfo.class);
+        final SubscriptionInfo sub2 = mock(SubscriptionInfo.class);
+        when(sub1.getSubscriptionId()).thenReturn(11);
+        when(sub2.getSubscriptionId()).thenReturn(22);
+        SubscriptionUtil.setAvailableSubscriptionsForTesting(Arrays.asList(sub1, sub2));
+
+        ShadowSubscriptionManager.setDefaultVoiceSubscriptionId(11);
+        ShadowSubscriptionManager.setDefaultSmsSubscriptionId(11);
+        ShadowSubscriptionManager.setDefaultDataSubscriptionId(11);
+        when(mTelephonyManager.getDataState()).thenReturn(TelephonyManager.DATA_DISCONNECTED);
+        when(mTelephonyManager.isDataEnabled()).thenReturn(false);
+
+        assertThat(mController.getSummary(11)).isEqualTo(
+                mContext.getString(R.string.default_for_calls_and_sms) + System.lineSeparator()
+                        + mContext.getString(R.string.mobile_data_off));
+
+        assertThat(mController.getSummary(22)).isEqualTo(
+                mContext.getString(R.string.subscription_available));
+    }
+
+    @Test
+    public void getSummary_twoSubsOneForCallsAndDataOneForSms() {
+        final SubscriptionInfo sub1 = mock(SubscriptionInfo.class);
+        final SubscriptionInfo sub2 = mock(SubscriptionInfo.class);
+        when(sub1.getSubscriptionId()).thenReturn(11);
+        when(sub2.getSubscriptionId()).thenReturn(22);
+        SubscriptionUtil.setAvailableSubscriptionsForTesting(Arrays.asList(sub1, sub2));
+
+        ShadowSubscriptionManager.setDefaultDataSubscriptionId(11);
+        ShadowSubscriptionManager.setDefaultSmsSubscriptionId(22);
+        ShadowSubscriptionManager.setDefaultVoiceSubscriptionId(11);
+        when(mTelephonyManager.getDataState()).thenReturn(TelephonyManager.DATA_DISCONNECTED);
+        when(mTelephonyManager.isDataEnabled()).thenReturn(true);
+
+        assertThat(mController.getSummary(11)).isEqualTo(
+                mContext.getString(R.string.default_for_calls) + System.lineSeparator()
+                        + mContext.getString(R.string.default_for_mobile_data));
+
+        assertThat(mController.getSummary(22)).isEqualTo(
+                mContext.getString(R.string.default_for_sms));
+    }
 }