Paulinho scored his first goal for Barcelona late in the second half of a 2-1 win over Getafe, upholding the club's perfect start to the Spanish league on Saturday.
Barcelona's fourth straight win opened a three-point lead over Real Sociedad, the only other team which entered the weekend with a perfect record. Real Sociedad hosts defending champion Real Madrid on Sunday.
Paulinho netted the winner after fighting off a defender inside the area and firing a right-footed cross shot into the far corner.
"I'm very happy to have scored the winning goal, it was very special," Paulinho said. "It was a difficult match and we got the three points, which was the most important thing."
A former Tottenham player who was playing in China last season, Paulinho was one of the few players signed by Barcelona in the offseason. The club paid 40 million euros to attract the Brazil midfielder and was criticized by many for spending so much on him.
Getafe, which has won only one of its four games, led through Japanese midfielder Gaku Shibasaki just before halftime.
Denis Suarez equalized in the second half.
"We had the game under control," Getafe coach Jose Bordalas said. "The players are disappointed. We put in a great effort. It doesn't seem like it was a fair result. We were unlucky."
Barcelona won the match but lost Ousmane Dembele, its biggest offseason signing, midway through the first half because of an apparent muscle injury.
The victory gave Barcelona a seven-point lead over defending champion Madrid.