She flew twice on the Columbia space shuttle: on the second US Microgravity Science Laboratory mission in October 1995; and on the deployment of the Chandra X-Ray Observatory in July 1999. She also spent six months aboard the International Space Station in December 2010, serving as the lead science officer, lead robotics officer, and flight engineer for Expedition 26/27. After 24 years of service, and having spent a total of 180 days in space, Coleman retired from NASA in December 2016.