From January 20, 2021 to February 2, 2021 he served as acting secretary of homeland security, during the Senate confirmation of Alejandro Mayorkas.

He earned his Bachelor of Science degree in ocean engineering from the United States Coast Guard Academy in New London, Connecticut.

From 1999 to 2001, he commanded Coast Guard Group/Marine Safety Office (now Sector) Long Island Sound, based in New Haven, Connecticut.

Vice Admiral Pekoske served as Commander, Pacific Area/Coast Guard Defense Forces West in Alameda, California.

He oversaw the operation of units performing missions in marine safety, maritime mobility, protection of natural resources, maritime security, homeland security and national defense in an Area of Operations encompassing over 73,000,000 square miles (190,000,000 km2) throughout the Pacific Basin and Far East.

[13] On November 13, 2019, with the appointment of Ken Cuccinelli as Acting Deputy Secretary, Pekoske returned to his duties as TSA Administrator.

From January 20, 2021 to February 2, 2021, Pekoske was appointed acting secretary of homeland security by President Joe Biden, during the Senate confirmation of Alejandro Mayorkas to the role.