The Seattle Mariners were designated as the Padres' interleague rivals when interleague play began in the 1990s. The rivalry was non-existent before this title was given. It is any loyal Gaslampballer's duty to promote this rivalry and pretend that it is important, even though it really means nothing to anybody.
- In July 1995 at the trading deadline, the Padres sent their ace Andy Benes to the Mariners for prospects P Ron Villone and OF Marc Newfield. Minor league P Greg Keagle was later sent to the Mariners to complete the trade. Benes was going be a free agent that offseason and the Padres were hoping to cash in on his value to get some building blocks for the future. The players Padres received never produced much in San Diego, but were both used to acquire slugger Greg Vaughn en route to the playoffs in 1996.
- In February 2000, the Padres acquired a new starting LF when they got Al Martin from the Mariners in exchange for P Tom Davey and 1B/OF John Mabry.
- In December 2001, the Mariners gambled on 1995's 2nd overall pick C Ben Davis as well as the light hitting INF Alex Arias and pitching prospect Wascar Serrano and gave up the struggling fireballer Brett Tomko, backup C Tom Lampkin, SS prospect Ramon Vasquez and cash.
- In January 2004, the Mariners acquired C Wiki Gonzalez, INF Dave Hansen, P Kevin Jarvis and minor league OF Vince Faison from the Padres for 3B Jeff Cirillo, P Brian Sweeney and cash. This was a Kevin Towers sludge merchant deal. The Padres had overpayed for Jarvis and no longer wanted him in the rotation, so they took on a similarly expensive contract in Cirillo's, but figured they could use him in a bench role while also acquiring a young bullpen arm in Sweeney.
- In Junly 2014, the Mariners acquired OF Chris Denorfia in exchange for OF Abraham Almonte and P Stephen Kohlscheen.