The Seattle Mariners 1997 season was their 21st since the franchise creation, and ended the season finishing 1st in the American LeagueWest, finishing with a record of 90-72. For the second straight regular season, they led the AL in runs scored (925) and shattered the all-time record for most home runs hit by a team in one season (set at 257 by the Baltimore Orioles just one season earlier) with 264. Five Mariners scored at least 100 runs and six hit at least 20 home runs. In addition, the Mariners pitching staff struck out 1,207 batters during the regular season: more than any other AL team.
In 1997, Randy Johnson set an American League record for left-handers by striking out nineteen batters in a 4-1 loss to the Oakland A's on June 24. On August 8 he matched the feat by setting down nineteen Chicago White Sox. Johnson posted a 20-4 record with 291 strikeouts and an ERA of 2.28. He finished second in the Cy Young balloting to Toronto's Roger Clemens.
July 17, 1997: Josías Manzanillo was released by the Seattle Mariners.
July 31, 1997: Heathcliff Slocumb was traded by the Boston Red Sox to the Seattle Mariners for Derek Lowe and Jason Varitek.
July 31, 1997: Paul Spoljaric was traded by the Toronto Blue Jays with Mike Timlin to the Seattle Mariners for Jose Cruz.
August 20, 1997: Roberto Kelly was traded by the Minnesota Twins to the Seattle Mariners for players to be named later. The Seattle Mariners sent Joe Mays (October 9, 1997) and Jeromy Palki (minors) (October 9, 1997) to the Minnesota Twins to complete the trade.
September 2, 1997: Steve Decker was released by the Seattle Mariners.