Offseason
- November 17, 1999: Rich Butler was signed as a free agent by the Mariners.
- December 15, 1999: John Olerud was signed as a free agent by the Mariners.
- January 14, 2000: Brian Lesher was signed as a free agent by the Mariners.
- January 19, 2000: Joe Oliver was signed as a free agent by the Mariners.
- February 10, 2000: Ken Griffey, Jr. was traded by the Mariners to the Cincinnati Reds for Mike Cameron, Brett Tomko, Antonio Pérez, and Jake Meyer (minors).
Read more about this topic: 2000 Seattle Mariners Season