- New York Mets traded Amos Otis and Bob Johnson to the Kansas City Royals for Joe Foy on December 3, 1969.
- New York Mets purchased Jerry May from the Kansas City Royals on May 14, 1973.
- New York Mets traded Tom Hall to the Kansas City Royals for Bryan Jones on May 7, 1976.
- New York Mets sold Ken Sanders to the Kansas City Royals on September 17, 1976.
- New York Mets traded Kevin Kobel to the Kansas City Royals for Randy McGilberry on June 17, 1980.
- New York Mets traded Juan Berenguer to the Kansas City Royals for Marvell Wynne and John Skinner on March 31, 1981.
- New York Mets signed free agent Jerry Martin of the Kansas City Royals on March 17, 1984.
- New York Mets traded Tucker Ashford to the Kansas City Royals for Tom Edens on April 1, 1984.
- New York Mets traded Tim Leary to the Kansas City Royals for Frank Wills on January 18, 1985.
- New York Mets traded Ed Hearn, Rick Anderson and Mauro Gozzo to the Kansas City Royals for David Cone and Chris Jelic on March 27, 1987.
- New York Mets traded Terry Leach to the Kansas City Royals for Aguedo Vasquez on June 9, 1989.
- New York Mets traded Archie Corbin to the Kansas City Royals for Pat Tabler on August 30, 1990.
- Kansas City Royals signed Dan Schatzeder of the New York Mets as a free agent on December 4, 1990.
- New York Mets traded Gregg Jefferies, Kevin McReynolds and Keith Miller to the Kansas City Royals for Bret Saberhagen and Bill Pecota on December 6, 1991.
- New York Mets traded Vince Coleman to the Kansas City Royals for Kevin McReynolds on January 5, 1994.
- New York Mets traded Jason Jacome and Allen McDill to the Kansas City Royals for Derek Wallace, John Carter and Geno Morones on July 21, 1995.
- New York Mets traded Al Shirley to the Kansas City Royals for Brent Mayne on December 19, 1995.
- New York Mets signed free agent Craig Paquette of the Kansas City Royals on December 23, 1997.
- New York Mets purchased Jermaine Allensworth from the Kansas City Royals on August 10, 1998.
- New York Mets sold Tim Spehr to the Kansas City Royals on August 31, 1998.
- New York Mets traded Jonathan Guzman to the Kansas City Royals for Shane Halter on March 23, 1999.
- New York Mets traded Derek Wallace to the Kansas City Royals for Jeremy Jackson on August 13, 1999.
- New York Mets traded Dan Murray to the Kansas City Royals for Glendon Rusch on September 14, 1999.
- New York Mets traded Endy Chavez to the Kansas City Royals for Mike Curry on March 30, 2001.
- New York Mets traded Graeme Lloyd to the Kansas City Royals for Jeremy Hill on July 28, 2003.
- New York Mets traded Jaime Cerda to the Kansas City Royals for Shawn Sedlacek on January 26, 2004.
- Kansas City Royals signed Doug Mientkiewicz of the New York Mets as a free agent on December 16, 2005.
- New York Mets traded Jeff Keppinger to the Kansas City Royals for Ruben Gotay on July 19, 2006.
- New York Mets traded Brian Bannister to the Kansas City Royals for Ambiorix Burgos on December 6, 2006.
- Kansas City Royals signed Brian Lawrence of the New York Mets as a free agent on February 1, 2008.
- Kansas City Royals claimed Joaquin Arias of the New York Mets on waivers on November 4, 2010.
- Kansas City Royals signed Dillon Gee of the New York Mets as a free agent on December 14, 2015.
- New York Mets signed free agent Jason Vargas of the Kansas City Royals on February 18, 2018.
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