The 29-year-old player was arraigned on charges of simple assault, harassment and disorderly conduct and freed on $10,000 bail.
"We're extremely disappointed with this incident," team chairman Dan Rooney said. "The Steelers do not condone violence of any kind, especially against women."
Wilson apologized and said he will be treated for anger management.
"I shouldn't have done it. I hold myself to a higher standard than that," he told the Pittsburgh Tribune-Review. "I just want to apologize to Lindsey, her family, the NFL family and the Pittsburgh Steeler nation. I let them down."
Lindsey Paulat told police that Wilson pushed her on the shoulder at the Patron Mexican Grill on Wednesday night. She said when she turned around he punched her in the left side of her face, according to the complaint.
Her left cheek was red and swollen, and witnesses told officers what happened, police said. Officers later found Wilson as he was leaving his Pine Township home in his car.
Wilson said he would attend anger management classes "to better myself for my child and my other children. It's tough to even talk about because I'm a man that's always tried to keep my nose clean."
Wilson's attorney, Paul Goltz, is out of the country. A woman at Goltz's office said the lawyer handling the case would not comment. Wilson's agent, Tom Condon, did not return calls.
Earlier this month, Steelers linebacker James Harrison was charged with hitting his girlfriend. He has a preliminary hearing April 3 and remains with the team.
Team spokesman Dave Lockett said Harrison's dispute began when he argued with his girlfriend about whether to baptize his son.
"In no way do we condone domestic violence of any kind," Rooney said in a statement Thursday evening. "Each incident must be considered on a case-by-case basis. In the situation with James Harrison, he contacted us immediately after his incident and has taken responsibility for his actions."
Harrison "said his conduct was wrong and he was embarrassed to be associated with the label of a perpetrator of domestic violence," Harrison's attorney, Robert Del Greco, said Thursday. Harrison then quickly sought anger management counseling, which he still attends, Del Greco said.
Wilson and the woman he's accused of hitting were also involved in a fight in January.
Police charged her with firing two gunshots after Wilson left his town house. Paulat, who is also the mother of Wilson's 1-year-old daughter, is awaiting trial.
Wilson, a backup, signed with the Steelers as a free agent from San Francisco in 2005. He caught 81 passes for 1,162 yards and two touchdowns in three seasons with the Steelers.