The 1988 Seattle Mariners season was their twelfth since the franchise creation and their home ballpark was the Kingdome in Seattle, Washington. The M's finished seventh (last) in the American League West with a record of 68–93 (.422). Manager Dick Williams, who later was inducted into the Hall of Fame, was fired in early June; first base coach Jim Snyder was promoted to interim manager in his only season as an MLB manager.

Note: Pos = Position; G = Games played; AB = At bats; H = Hits; Avg. = Batting average; HR = Home runs; RBI = Runs batted in

Note: 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

AZL club affiliation shared with Boston Red Sox