Install Android 6.0.1 Marshmallow on T-Mobile Galaxy S3 T999 [CM13]



Android 6.0.1 Marshmallow firmware via unofficial CyanogenMod 13 custom ROM is now available for T-Mobile Galaxy S3 T999. We have already posted an article on flashing Android 6.0.1 Marshmallow for Galaxy S3 i9300 and in this tutorial we are going to follow the same procedure we used earlier. The CM13 ROM is based on Android 6.0.1 Marshmallow with all the latest feature and redesigned interface, T-Mobile Galaxy S3 T999 is an old device which is not present in the list of devices receiving the official Marshmallow updates from Samsung. So the AOSP Marshmallow ROM is the only choice left for the users of Galaxy S3 to install and experience the glimpse of latest firmware on their device.

Note: The Android 6.0.1 Marshmallow ROM for T-Mobile Galaxy S3 T999 is currently in the testing stages and you may experience some bugs but most of the features are seems to be working fine. If you are interested to install Android 6.0.1 Marshmallow ROM on your T-Mobile Galaxy S3 T999 then just go ahead and follow the below description.

Also Read: Update T-Mobile Galaxy S3 on Stagefright fix T999LUVUBOH1 firmware

How to install Android 6.0.1 Marshmallow on T-Mobile Galaxy S3 T999 via CM13 ROM

Before you Begin:

Disclaimer: This tutorial includes multiple operations including Custom Rom, custom recovery etc. Follow the guide on your own risk, we are not responsible if you brick or damage your device however the chances of bricking a device are rare but you have to pay full attention on the complete guide to avoid any issues and difficulties while performing any of the above mentioned operation.


  • Please ensure your phone battery should be charged at minimum 80%
  • Download Samsung USB drivers
  • Your device should have a working TWRP or CWM recovery installed in your device.

Necessary downloads:

Process to install Android 6.0.1 Marshmallow on T-Mobile Galaxy S3 T999

Connect your device to your PC and copy the both ROM and google apps zip files onto your device storage.

Turn of your device and boot into TWRP custom Recovery menu by the hardware keys combination or using any third party app (Mostly found in Play store).

Once your device enters into TWRP recovery, create a Nandroid backup of your device or follow our guide to create a Nandroid backup (this will create a backup of your complete device including current firmware) if something goes wrong you can restore your previous firmware.

Once the Nandroid process completes, tap on “Wipe” and then swipe the slider from left to right to begin the wipe process (This will reset your device to factory)

Now it’s the time to flash the Marshmallow firmware on your device. Choose install and navigate to the folder in which you have copied the Marshmallow zip file

Swipe across the slider to confirm install, wait for a few minutes till the file is completely installed in your device.

Once done with the above step, now apply the same process with the installation of gapps.

Wait for the installation process to complete.

Once completed Reboot your device.

If your device is taking longer then 7-10 minutes then follow this guide to to fix this issue

That’s it! You have successfully installed Android 6.0.1 Marshmallow via Unofficial CM13 ROM on T-Mobile Galaxy S3 T999. If you have any query feel free to contact us by posting your queries in the below provided comment section. Follow us on Facebook/Twitter/Google+ for future update.

A Software Engineer who loves to hang around latest gadgets and writes his own experiences to get the best possible and accurate information.

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