Victorino and Howard each hit two-run homers, Jimmy Rollins had a go-ahead triple in the sixth, and Philadelphia salvaged a split of its four-game series.
Cole Hamels (4-1), the Phillies' talented young pitcher, struck out nine to win his second straight start and also had a double in the sixth for his second hit of the year and first for extra bases. Rollins followed with his third triple of the series off reliever Vinnie Chulk (0-2).
The 22-year-old Lincecum, a hard-throwing righty selected 10th overall in the 2006 draft, struck out five and walked five. He allowed five runs -- four earned -- and five hits in 4 1-3 innings. He went 4-0 with a 0.29 ERA in five starts for Triple-A Fresno, allowing one earned run in 31 innings, and was called up sooner than the organization planned only a year after he was in college. He made eight starts at two levels of A-ball last year.
He became the fourth player from last year's draft to reach the majors, joining Detroit's Andrew Miller, Joe Smith of the New York Mets and Seattle's Brandon Morrow.
Lincecum spent spring training in big league camp, so the Giants expected him to be comfortable and unfazed right away. He is the fifth-fastest drafted Giants player to reach the big leagues.
Victorino hit his first homer of the year in the first following a leadoff single by Rollins. Howard connected two innings later after a two-out walk to Chase Utley. The Phillies provided the power on a night San Francisco slugger Barry Bonds had off to rest a day after hitting his 744th career homer.
Victorino went 10-for-17 (.588) with four multihit games and four RBIs in the series.
Omar Vizquel doubled in a run in the second for his 2,500th career hit, becoming the 83rd player in major league history to reach the mark, and Rich Aurilia and Kevin Frandsen had two hits apiece.
Lincecum's first four pitches to Rollins were clocked at 97 mph, 98, 97 and 96 on the single. He reached 98 again to Victorino before hitting 100 on the stadium gun against Utley before striking him out.
Lincecum struck out the side in the first, bouncing off the mound after retiring Aaron Rowand.
Lincecum had a 19 2-3 innings scoreless streak to start the season for Fresno. San Francisco didn't hesitate to bring him up to fill in for fifth starter Russ Ortiz, on the disabled list with an irritated nerve in his elbow.
"He's done so well, why not now?" Giants general manager Brian Sabean said. "How ready he is or what he's going to look like tonight is anybody's guess."
Lincecum received a standing ovation when he walked off the mound in the fifth after issuing Pat Burrell's third of four walks, giving way to Chulk following a 100-pitch performance -- right on his pitch limit.
"You'd like to think he's up here for good, but there are no guarantees," Sabean said.
Hamels gave up five runs, three earned, and eight hits in seven innings. Brett Myers finished for his second save.
Dusty Baker worked the game in the broadcast booth doing radio for ESPN and received a standing ovation when shown on the big screen in the sixth. The former Giants manager stood and waved.
Notes: Burrell walked four times in a game for the second time in his career. He last did it in 2005. Michael Bourn ran for him in the seventh, then stole second and third. ... Phillies 3B Wes Helms had two errors. ... With Linden playing CF for the Giants, Linden and Lincecum marked the second time in major league history two former University of Washington players were in the starting lineup. Chris Magruder played LF and Aaron Myette pitched for the Rangers on Sept. 10, 2001. ... It was 83 degrees at first pitch.