The win gave the Blue Jays (15-21) their first three-game winning streak of the season. The Mariners (17-19) have lost two in a row.
Devon Travis also had two RBIs for the Blue Jays, who are assured of at least a split in the four-game series.
Biagini (1-1), who made his second career major-league start, allowed four hits, no walks and no runs. The right-hander struck out three.
Seattle starter Christian Bergman (0-1) allowed seven hits, one walk and three runs in five innings. He had one strikeout.
Biagini left after surrendering a leadoff single in the sixth to Jean Segura, who extended his hitting streak to 11 games.
Aaron Loup replaced Biagini for one batter, inducing a grounder to third from Ben Gamel that forced Segura at second. Danny Barnes replaced Loup in the sixth and pitched around Kyle Seager's single.
The Blue Jays increased their lead to 4-0 against reliever Jean Machi in the sixth. Ryan Goins singled, took second on a passed ball, went to third on a single by Darwin Barney and came home on a sacrifice fly by Travis.
Guillermo Heredia and Taylor Motter started the seventh with singles against Barnes, who struck out Carlos Ruiz and Jarrod Dyson. Ryan Tepera replaced Barnes and ended the inning with Segura's fly to right and pitched a perfect eighth.
Roberto Osuna retired the side in order in the ninth.
The Blue Jays scored once in the second inning.
Steve Pearce and Goins each had a single and advanced a base after Barney's sacrifice. Pearce scored when Travis grounded out to shortstop.
Pearce made a diving catch in left field to end the top of the third on Gamel's attempt for a hit with runners at second and third.
Bautista gave Toronto a 3-0 lead with his fourth homer of the season, a two-run shot with one out in the third. It scored Kevin Pillar, who led off with a single.
NOTES: Seattle 2B Robinson Cano (right quadriceps strain) missed his second straight game. He left the game Tuesday in Philadelphia with the injury in the fourth inning, played Wednesday against the Phillies and was a late scratch Thursday. INF Taylor Motter started at second base. ... Toronto DH Kendrys Morales (tight left hamstring) missed his third straight game. He left the game Tuesday in the seventh inning with the injury. RF Jose Bautista was DH for the second straight game with OF Ezequiel Carrera in right field. ... Seattle OF Guillermo Heredia started in left field after missing the start Thursday because of visa issues entering Canada. ... Toronto RHP Marcus Stroman (3-2, 3.38 ERA) will oppose LHP Dillon Overton (0-0, 6.17) on Saturday in the third game of the four-game series.