The Brazilian defender scored from a freekick after 18 minutes but his side failed to make the most of a second yellow card for Espanyol's Wakaso Mubarak in the 68th, and endured some shaky moments before securing the victory.
Betis climbed to nine points from four games, three short of leaders Barcelona, who were hosting Granada in the late game.
Earlier, South Korea striker Park Chu-young (pictured) scored with his first touch on his home debut for promoted Celta Vigo, leading them to a 2-1 victory over Getafe.
Park, who helped his country win bronze at the Olympic Games in London and joined Celta on loan from Arsenal on transfer deadline day three weeks ago, volleyed home in the 68th minute.
Celta had taken the lead in the 57th with a breakaway goal from Augusto Fernandez, only for Abdelaziz Barrada to level almost immediately after a well-worked move.
Park, who netted two minutes after coming off the bench, had the chance to score a second near the end but he pulled his shot wide with only the keeper to beat.
Celta's second win put them ninth in the standings with six points from five games, two places ahead of Real Zaragoza, who won 3-1 at home to bottom side Osasuna.
Osasuna finished seventh last season but have only taken one point from 15 this term and trail Espanyol who also have one point. But they did score the goal of the game at the Romareda with Emiliano Armenteros's run and shot after 29 minutes.