During the First World War, he enlisted as a private in the Fifth Regiment, United States Marine Corps, and served from August 9, 1917, until honorably discharged on April 1, 1919. He received the Purple Heart Medal.
After the war, Imhoff attended the Ohio State University in Columbus. He served as the clerk of courts for Belmont County, Ohio, from 1921 to 1925. He studied law and was admitted to the bar in January 1930. He served as probate judge of Belmont County 1925-1933.
Imhoff was elected as a Democrat to the Seventy-third, Seventy-fourth, and Seventy-fifth Congresses (March 4, 1933-January 3, 1939). He was an unsuccessful candidate for reelection in 1938 to the Seventy-sixth Congress. He served as special assistant to the United States Attorney General in 1939 and 1940.
With World War II raging, Imhoff was commissioned as a lieutenant commander in the United States Navy Reserve on January 21, 1943. He was promoted to rank of commander and released from active duty on November 8, 1945.