Serrano's first career home run came off Aztecs reliever Justin Hepner after Brett McAfee struck out and Jacob Mahan grounded out in the ninth. Serrano connected on a 1-0 fastball, sending it over the left-center field wall.
Arkansas (9-5) had tied the game in the bottom of the seventh inning on a Tyler Spoon RBI single to plate Mahan. Spoon, who finished the game with two hits, extended his hit streak to 14 games.
San Diego State (7-7) took a 2-0 lead on a Matt Munoz two-run home run with two outs in the top of the second inning. Arkansas starter Ryne Stanek walked the next three batters before stranding the bases loaded.
Arkansas picked up Stanek with a pair of two-out runs during a wild sequence in the bottom of the third inning.
Mahan scored when a wild pitch allowed Willie Schwanke to walk. Schwanke then got caught in a rundown between first and second, allowing Serrano to score from second base when San Diego State second baseman Tim Zier overthrew his catcher.
Schwanke eventually ended up on third base, but was stranded to end the inning. The Razorbacks left eight runners on base.
San Diego State regained the lead on a Brad Haynal RBI double in the fifth inning. Arkansas preserved the 3-2 deficit when Jacob Morris threw out Haynal at the plate.
The Aztecs loaded the bases in the seventh against Arkansas relievers Trent Daniel and Colby Suggs, but couldn't extend their lead when Jalen Beeks struck out two consecutive batters to end the inning. San Diego State stranded 11 runners Friday.
Spoon's seventh inning RBI chased Aztecs starter Philip Walby. The right-hander allowed three runs on six hits in 6 1/3 innings.
The two teams will play a doubleheader Saturday beginning at 11:35 a.m. Arkansas will throw freshman right-hander Trey Killian in the first game and senior left-hander Randall Fant in the series finale.