Under second-year manager Jim Lefebvre, they finished fifth in the American League West at 77–85 (.475).
It was the second-best record in the M's history up to that point in time; the win total was one behind the club record set in 1987.
[1] The Mariners hit six grand slams, the most in MLB in 1990.
Infielders Coaches August 31, Kingdome, Seattle, Washington Note: Pos = Position; G = Games played; AB = At bats; H = Hits; Avg.
= Batting average; HR = Home runs; RBI = Runs batted in Note: G = Games pitched; IP = Innings pitched; W = Wins; L = Losses; ERA = Earned run average; SO = Strikeouts Note: G = Games pitched; IP = Innings pitched; W = Wins; L = Losses; ERA = Earned run average; SO = Strikeouts Note: G = Games pitched; W = Wins; L = Losses; SV = Saves; ERA = Earned run average; SO = Strikeouts