This history is relatively young.
- July 27, 2018: The Cardinals traded Sam Tuivailala to the Seattle Mariners for Seth Elledge.
- July 21, 2017: The Cardinals traded Marco Gonzales to the Seattle Mariners for Tyler O’Neill.
- December 12, 2010: The St. Louis Cardinals traded Brendan Ryan to the Seattle Mariners for Maikel Cleto.
- November 9, 1979: The Seattle Mariners purchased Dan O’Brien from the St. Louis Cardinals.
- June 7, 1979: The Seattle Mariners purchased Rob Dressler from the St. Louis Cardinals.
- June 26, 1978: The Seattle Mariners traded Jose Baez to the St. Louis Cardinals for a player to be named later. TheSt. Louis Cardinals sent Mike Potter (October 27, 1978) to the Seattle Mariners to complete the trade.