Lieutenant Colonel Karen Anne McCrimmon was born in Weston, Ontario. Her father, Charles Martin, was a metallurgic technician employed by the A.V.Roe Company working on the AVRO Arrow CF-105. Her mother, Isabel, emigrated from Scotland on her own, at the age of 20. When the Arrow project was cancelled in 1959, her father found work with Trans-Canada Airlines and moved his family to Timmins, Ontario. In 1971, the family moved to Windsor, Ontario.
While in high school, McCrimmon joined the Royal Canadian Army Cadets. In 1975 she joined The Windsor Regiment (RCAC) as a Reservist. She graduated with a Bachelor of Arts from the University of Windsor in Russian and Linguistics. McCrimmon then joined the Regular Force in 1980, and became an air navigator, the first female to gain such a qualification.
In 1995, she was made a member of the Order of Military Merit, and in 1998 was promoted lieutenant-colonel, and given command of 429 Transport Squadron, becoming the first woman to command a Canadian Forces flying squadron. In 2000 she headed the Transport and Rescue Standardization and Evaluation Team. In July 2006 she was posted to Ramstein, Germany to serve as a Senior Staff Officer at the NATO Air Headquarters. She did a tour of duty in Afghanistan in 2004 where she was responsible for NATO Airlift Co-ordination. She retired from the Forces in 2006.
McCrimmon became involved in federal politics with the Liberal Party in 2008. She was the Liberal candidate for the riding of Carleton-Mississippi Mills in the 2011 federal election, but lost to the Conservative incumbent Gordon O’Connor. In December 2012 she announced her bid for the leadership of the Liberal Party of Canada, and on April 14, 2013 she conceded to the winner Justin Trudeau.
McCrimmon studied facilitation, negotiation and mediation at Harvard Law School, completing the program in 2008. She now acts as a consultant for private and public institutions and organizations.
Married to Rob McCrimmon since 1985, the couple have two grown children. McCrimmon is a private pilot and is a member of the Women's Executive Network (WXN), CFUW, FMWC, Royal Canadian Legion, and CWIA.