In his first start since being acquired on Tuesday, the right-hander hurled 5 1/3 shutout innings, holding the Giants to five hits and three walks, while striking out 10 in the Cubs' 8-7 victory.
Harden didn't get a win, but he got a nice parting gift, a deafening standing ovation from 41,000 strong upon his exit.
"I never really had anything like that pitching in Oakland," said Harden, who made 97 starts for the Athletics beginning in 2003. "It was really cool to see."
Cubs manager Lou Piniella said he wanted to keep Harden to 90 to 110 pitches before the game. Harden threw 96, including 66 for strikes and didn't show signs of decreasing velocity that had been a concern in previous outings.
Harden got off to a fast start, fanning five hitters in the first three innings, but put runners on in each frame while he adapted to the atmosphere.
"I didn't really know what to expect going in," Harden said. "I just wanted to go out and treat it like any other start -- at least try to. It was exciting. I had a lot of adrenaline going the first couple innings. I just wanted to get through the first couple and calm myself down."
Catcher Geovany Soto didn't notice any nerves.
"We clicked right away, and he was moving that fastball around the place, and his changeup was outstanding," Soto said. "He did a great job -- and he's going to be huge for us."
The 12-pitch fourth was simply filthy. Aaron Rowand, John Bowker and Rich Aurilia struck out in succession. Harden gave up two singles in the fifth and put the first two hitters on in the sixth, bringing Piniella to the mound.
Piniella delighted the fans and kept Harden in. That allowed the Cubs' biggest in-season pitching acquisition since Henry Rowengartner ("Rookie of the Year") to end his day on a high note, a foul-tip strikeout of Bowker.
Harden departed with a seven-run lead, but relievers Kevin Hart and Carlos Marmol couldn't hold it. He recorded the third double-digit strikeout game of his career and lowered his ERA to 2.19.
"It's a shame," Piniella said. "Harden pitched really, really well."
Harden shrugged off the no-decision.
"I would have liked to go a little deeper in the game, but I threw a lot of pitches, got behind some hitters, walked a few guys and gave up some two-strike hits, which I don't like to do," Harden said. "My pitch count didn't allow me to [stay in the game], but it was a good game. The guys came back in the last inning there. You never want it to end up like that, but the important thing is the team won."
Don't get too excited. Harden still has a lot to learn about the National League, hitting in particular. He struck out in all three of his at-bats and was unable to get a bunt down with a runner on first and one out in the second.
He has time to work that out. His next start isn't until July 21. Harden can spend the All-Star break soaking it in.
"I had a lot of people telling me it was going to be a good experience," he said, smiling. "It was."
Nick Zaccardi is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.