Matt Kemp added two hits for the Dodgers, who moved within 1 1/2 games of the Pirates for one of the two National League wild card spots. Aaron Harang (8-7) pitched six effective innings to snap a modest two-game losing streak while Kenley Jansen worked a perfect ninth for his 24th save.
Victorino, acquired in a trade from Philadelphia two weeks ago, hit his first homer in a Dodgers uniform in the fifth. The two-run shot off Jeff Karstens (4-3) broke a 2-2 tie as Los Angeles beat the Pirates for the seventh straight time.
Garrett Jones had four hits and drove in all three Pirate runs. Pittsburgh has dropped four of five.
The Dodgers, meanwhile, have won four of five to close in on San Francisco for the NL West lead. The surge has been powered by the slew of new arrivals acquired to give the team a needed boost.
Shortstop Hanley Ramirez played lights out over the weekend as the Dodgers took a weekend series in Miami. On Monday, it was Victorino's turn. The two-time All-Star has feasted on Pittsburgh's pitching throughout his career. He came in with a .325 career batting average against the Pirates, a number that quickly rose against Karstens.
Victorino doubled to right with one out in the third to put Los Angeles on the board, then raced home two batters later on an RBI-single by Kemp. Jones tied it up in the bottom of the inning with a two-run double that scored Starling Marte and Andrew McCutchen.
It didn't stay tied for long.
Harang singled with one out in the fifth and Victorino turned on a Karstens pitch and sent it into the right-field seats for his first homer since July 29, Victorino's last game with Philadelphia. The Dodgers are hoping his quick bat and playoff experience will help Los Angeles return to the postseason after a three-year absence.
He certainly provided it against the Pirates while Harang put together a typical steady outing. The right-hander was virtually flawless against everybody not named Jones, giving up two runs on five hits in six innings, walking three and striking out four to improve to 15-6 against Pittsburgh in his career.
Karstens, who hadn't lost since June 25, couldn't keep pace. Normally one of the most efficient pitchers in the game, Karstens needed 100 pitches to get through seven innings, giving up four runs on seven hits, striking out four and walking one.
The Pirates had several chances to tie it up. But Neil Walker lined out at reliever Randy Choate's head with two on to end the seventh. Run-scoring singles by Jones and Mike McKenry drew Pittsburgh within one in the eighth, but Clint Barmes grounded to third to end the threat.