Giambi opened with a three-run homer in the first. Abreu hit a two-run homer in the sixth and his two-RBI double was part of a five-run seventh.
Winner Mike Mussina (7-4) surrendered four earned runs on seven hits in five innings.
Seattle, which matched the Yankees' four-run second with four of its own in the third, got a three-run homer from Jose Vidro in the third, Adrian Beltre's solo blast in the same inning and Richie Sexson's two-run homer in the eighth.
The losing pitcher in the Mariners' fifth loss in a row was starter Carlos Silva (3-4).
Both Jose Lopez and Yuniesky Betancourt had three hits.