In a game of few chances, Loren Moron's second-half winner gave all three point to Betis at the expense of a plucky Girona side.
The first-half passed without incident, before Moron gave the visitors the lead on 64.
That seemed to spark the hosts into life and just two minutes later, Cristhian Stuani smashed a shot against the post.
A flurry of subs didn't alter the score line, with Joaquin coming closest to adding to Betis' solitary goal, also hitting the woodwork on 89.