Born in Firth, Idaho to Lily Dorothy Miriam (née Wahlquist) and Farrel L. Hansen, his mother the daughter of Swedish immigrants and his father of Danish descent.

He served in the U.S. Navy from 1944 to 1946, including one year in the Pacific on the aircraft carrier USS Saratoga, and was a member of the U.S. Air Force Reserve until his retirement as a lieutenant colonel in 1978.

In his first run for Congress in 1962, he won the GOP nomination in a June runoff,[6][7] but lost the general election to incumbent Ralph Harding.

He served three terms before being ousted in the 1974 Republican primary in August by the man he succeeded six years earlier, George Hansen (no relation).

Following his service in Congress, Hansen returned to private law practice, and founded the Columbia Institute for Political Research in 1977.