Yes, plecos can live with bettas. Even though bettas tend to be aggressive towards other fish, plecos won’t trigger their aggression. This is because plecos have a peaceful nature and dull coloration, so bettas don’t see them as a threat. Moreover, because plecos are bottom dwellers, they’ll mostly stay out of the betta’s way.
However, plecos are usually much bigger than bettas, so you can’t keep them in a small betta tank. Depending on the type of your pleco, you might need a 75-gallon tank or bigger to make sure they’re all happy and healthy.