He was elected as a Whig to the Twenty-sixth and Twenty-seventh Congresses for the eighth district of Tennessee.

He lost to future U.S. President Andrew Johnson, who received 67,499 votes in the gubernatorial election.

Gentry served in the Confederate States Congress during the American Civil War.

The Journal of the Confederate Congress supports this view, listing him as having taken his seat on March 17, 1862, with his last appearance being near the day the second session ended, October 13, 1862.

"[6] Gentry died in Nashville, Tennessee on November 2, 1866 (age 57 years, 48 days), at Clover Bottom, the home of his sister-in-law Mary Ann Hoggatt.