George Varnum Barrett was born on July 10, 1837, in Boston, Massachusetts, to Varnum and Susan Barrett. His father was a farmer who owned $1,500 of real estate and $1,800 of personal property by 1860. The family lived in Shirley, Massachusetts, and by 1860, he was working as a farm laborer.
He enlisted in the Union army on May 29, 1861, and he mustered in as a private in Company B of the 6th Massachusetts Militia Infantry on June 19. According to his service records, he was 5 feet, 9 ½ inches tall, with brown hair and gray eyes. The regiment helped defend Washington, D.C., and he mustered out on August 2, 1861.
He returned to the army on September 28, 1861, mustering in as a sergeant in Company E of the 23rd Massachusetts Infantry. The regiment took part in the Battle of Cold Harbor and the siege of Petersburg. He was promoted to 2nd lieutenant in January 1863 and to 1st lieutenant in October 1863. He mustered out on September 28, 1864.
He moved to Groton, Massachusetts, after leaving the army. By 1870, he was working as a railroad ticket master. He married Ellen Augusta Johnson on August 9, 1876, and they apparently had no children. They lived in Ayer, Massachusetts. His wife died in 1896. He applied for a federal pension in December 1906 and eventually received one. He died of arteriosclerosis in Ayer on November 4, 1912.