iOS Icons
- Set
AppIconinImages.xcassets. - Add 9 different size icons:
29pt29pt*229pt*340pt*240pt*357pt57pt*260pt*260pt*3.
Images.xcassets will look like this:

Android Icons
- Put
ic_launcher.pngin folders[ProjectDirectory]/android/app/src/main/res/mipmap-*/.- 72*72
ic_launcher.pnginmipmap-hdpi. - 48*48
ic_launcher.pnginmipmap-mdpi. - 96*96
ic_launcher.pnginmipmap-xhdpi. - 144*144
ic_launcher.pnginmipmap-xxhdpi. - 192*192
ic_launcher.pnginmipmap-xxxhdpi.
- 72*72
Update 2019 Android
The latest versions of react native also supports round icon. For this particular case, you have two choices:
A. Add round icons:
In each mipmap folder, add additionally to the ic_launcher.png file also a round version called ic_launcher_round.png with the same size.
B. Remove round icons:
Inside yourProjectFolder/android/app/src/main/AndroidManifest.xml remove the line android:roundIcon="@mipmap/ic_launcher_round"and save it.
Otherwhise the build throws an error.