Pettitte threw 20 pitches in the simulated inning. If he doesn't feel any pain in his injured groin, Pettitte says he will report to the Yankees' minor-league complex in Tampa to throw a simulated game on Thursday.
Pettitte has been sidelined since July 18 with a strained left groin.
"Today was good," he said. "I pushed it and now I'm going to continue the process."
Pettitte said he threw warmup pitches on Monday and took a five-minute before throwing the simulated inning to mimic game conditions.
He felt some fatigue from "pushing it" but said it was nothing out of the ordinary. He reported no pain in his left groin.
Pettitte's only concern after Monday's session was his arm stamina. He will need at least one minor-league rehab start before returning to the Bronx.
"I'm not gonna come back here [too quickly] and do something stupid," he said. "If I don't feel comfortable in a rehab start or whatever I'll take an extra one because I don't want to aggravate this any more or hurt this any more.
Right-hander Dustin Moseley has filled in nicely for Petttitte. He allowed just two runs in 6 1/3 to earn the win in the Yankees' 7-2 victory over Boston on Sunday night.
But the Yankees will be happy to see Pettitte back in the rotation. The 38-year-old is enjoying one of the finest seasons of his 16-year career. He is 11-2 in 18 starts with a 2.88 ERA and was named to the All-Star team for the third time.
Ian Begley is a frequent contributor to ESPNNewYork.com.