With his father watching from the stands, Harrison homered, doubled, single and drove in a career-high five runs to lead the Pirates to a 8-3 win over the Milwaukee Brewers on Friday.
The Pirates are holding the team's annual Father & Son Weekend during this series, with the dads of numerous players, including Harrison's, on the trip.
Harrison's father sat near his locker in the clubhouse after the game with a big smile on his face.
''It is always special to play well in front of my dad,'' Harrison said. ''He's seen me play plenty of times, but you still always want to do well.''
Pirates manager Clint Hurdle said it ''was a big show up night'' for Harrison as each of three hits came with two outs.
''Those are game-changers,'' Hurdle said. ''It was a very big night for Josh. It was fun to watch.''
Andrew McCutchen also homered for Pittsburgh, which had lost nine of 12 going into the series against the NL Central-leading Brewers. With the win, Pittsburgh now trails Milwaukee by five games.
Jeff Locke (5-3) pitched six strong innings, giving up two runs and two hits. He walked six, but was able to strand five runners.
Yovani Gallardo (8-7) lasted just five innings, allowing six runs on eight hits and three walks.
Ryan Braun's two-run homer in the first inning gave Milwaukee a 2-0 lead. It was his 16th home run of the season, but just his second since July 22 as he's been slowed by a sore thumb.
Pittsburgh came right back in the second for 3-2 lead, taking advantage of Gallardo's wildness as he issued two straight walk after an error by third baseman Aramis Ramirez. Jody Mercer hit a sacrifice fly and Harrison lined a two-run double.
The Pirates made it 4-2 on Neil Walker's RBI triple in the third and Harrison singled home a run in the fourth.
McCutchen hit his 18th home run of the season leading off the fifth. It was his third game since coming off the disabled list because of a rib fracture and it was his first home run since he hit two against Cincinnati on July 12.
Harrison hit a two-run homer in the eighth.
WALK THIS WAY
The Pirates won despite issuing eight walks and recording only one strikeout. Hurdle said he cannot remember winning a game with those type of stats.
Pirates: Hurdle expressed cautious optimism that INF Clint Barmes would be able to rejoin the team during a three-game series with St. Louis that starts Monday. Barmes has been out since early July with a left groin strain and is currently on a rehab assignment with Triple-A Indianapolis.
Brewers: RHP Kyle Lohse, who missed his last start due to a sore right ankle, is set to start Monday against the San Diego Padres. Lohse threw a bullpen session Friday and said afterward he felt good. ... RHP Matt Garza (left oblique strain) will throw a bullpen session Sunday. Manager Ron Roenicke said he hopes Garza would return to the starting rotation in early September.
Pirates: RHP Edinson Volquez (10-7) starts Saturday at Miller Park. He has won six of his last seven decisions.
Brewers: RHP Wily Peralta (15-7), tied for the major league lead in wins, faces the Pirates.