Spain's all-time leading scorer with 51 goals, broke his left leg at the Club World Cup last December and missed the national team's Euro 2012 triumph as he continued his recovery.
He replaced Pedro in the 74th minute to a huge Nou Camp ovation and swept a shot inside the far post, after a pullback from Andres Iniesta, to crown his return with six minutes left.
"It has been a difficult time and it is nice to be back," Villa told Spanish television with a big grin.
"I am pleased to be able to say I can forget about the injury now. I have had five weeks training at the maximum level but my body still struggles to reach the levels necessary to play more minutes.
"I'll keep on working until I can eventually play a full game again."
Villa, 30, peeled away to celebrate, pulling off his shirt to reveal a vest with "Impossible without you" written on it above a photo of his wife and children.
"Because of me, I am sure it has been a difficult time for them as well," he added in reference to his dedication.
EL GUAJE
Barca midfielder Xavi led the tributes as soon as the game finished.
"He has suffered a lot, he has had a considerable injury and he is back," he told Spanish television.
"It was a good win but the best news of all is the return of 'El Guaje' ('The Kid'), we have missed him."
Barca were limited in their options going forward in the second half of last season with Villa injured and relied heavily on the goals of Lionel Messi.
The club decided not to strengthen the forward line in the transfer window and have focused on signing defensive reinforcements Jordi Alba and Alex Song, while waiting for Villa's return.
"I am happy with the squad we have," new Barca coach Tito Vilanova told a news conference after his first league match since stepping up from assistant to replace Pep Guardiola.
"We hope that Villa is back to full fitness as soon as possible because we are missing his goals.
"It is always important to win the first game but perhaps the best news today is the return of Villa.
"The goal will boost his morale and give him confidence. It has removed a weight from his shoulders. It's good for the team that he is back and well."
