After graduating from Villanova, Clancy worked as a history teacher for four years at the former Bishop Kenrick High School in Norristown, Pennsylvania, and then for a year at Father Judge High School in Philadelphia.[3]
Clancy joined the United States Secret Service in Philadelphia in the 1980s. Subsequently, he worked in the New York field office, directing a team of agents that conducted major investigations. He was in charge of security at national special events before joining the president's protective detail.[2]
During his work on the presidential protection details he was able to achieve a close bond with President Barack Obama, and was well regarded by the Obama administration. Clancy was part of the Secret Service protective detail that jogged with President Bill Clinton in the early days of his presidency.[4]
Clancy was appointed as acting director following the resignation of Julia Pierson on October 1, 2014, a position he held until his appointment as director on February 18, 2015 by President Obama.[5]
On February 14, 2017, Clancy announced his retirement, effective March 4, 2017.[6]