List of Seattle Mariners minor league affiliates

The following is a list of Seattle Mariners minor league affiliates. The first affiliate of the Mariners was the Short-Season A Bellingham Mariners in 1977. Since the Seattle franchise was included in Major League Baseball, they have had a total of 39 teams have been affiliated with the Mariners, and the longest team affiliated with Seattle is the Arizona League Mariners, and the Dominican Summer Mariners who were affiliated with Seattle for 21 seasons (from 1989–2010).

Fifteen teams have won league championship while affiliated with the Seattle Mariners. The most recent league champions are the Arizona League Mariners in 2008. The most a single minor league affiliated franchise had won is four; the Bellingham Mariners in 1977, 1980, 1986, and 1992. The Bellingham Mariners finished first in the Northwest League seven times while affiliated with Seattle (1979–1981, 1983, 1986, 1992–1993). In each league classification, the Seattle Mariners have been affiliated with 5 Triple-A teams, 11 Double-A teams, 7 Class-A teams, 10 Class-A Advanced teams, 2 Short-Season A teams, 4 rookie league teams, and 2 foreign rookie league teams.

The current structure of minor league baseball has been in effect since the 1990 season when the Class A level was subdivided for a second time with the creation of Advanced A. The Rookie level consists of domestic and foreign circuits, the latter based in the Dominican Republic and Venezuela.

The foundation of the minors' current structure was the result of a reorganization initiated by Major League Baseball (MLB) before the 1963 season. The reduction from six classes to four (AAA, AA, A and Rookie) was a response to the general decline of the minors throughout the 1950s and early-1960s when leagues and teams folded due to shrinking attendance caused by baseball fans' preference for staying at home to watch MLB games on television. The only change made within the next 27 years was Class A being subdivided for the first time to form Short Season A in 1966.

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