The original Mass Effect trilogy was being developed with Unreal Engine 3, but when it was time for Mass Effect: Andromeda, BioWare infamously changed it for DICE's in-house engine Frostbite 3. This required a lot of rework of assets, and contributed towards the very troubled launch of the game.
Now it seems like BioWare has decided to change engine again for Mass Effect 4 and is once again using Unreal Engine (which was also used for Mass Effect: Legendary Edition earlier this year), possibly even the latest version numbered 5. The source is BioWare's producer Brenon Holmes who tweeted this during the weekend:
"Bioware is hiring talented programmers with UE4/5 experience! Come, join our team and work with us on the next Mass Effect game!"
Earlier this month we got a little taste of what Unreal Engine 5 is capable of in the free The Matrix Awakens demo launched for PlayStation 5 and Xbox Series S/X. Hopefully, it's a taste of things to come, whenever the Mass Effect saga continues.