Brent was born in Ballinasloe, County Galway, Ireland on March 15, 1904,[1][2][3] to John J. and Mary (née McGuinness) Nolan.

[5][6] He fled Ireland with a bounty set on his head by the British government, although he later claimed only to have been a courier for guerrilla leader and tactician Michael Collins.

According to Ballinasloe Life (volume 2, issue 4, Oct/Nov 2012),[2] the Irish War of Independence careers of three different men named George Nolan (Brent and two others; one from County Dublin and the other from County Offaly) were apparently conflated, which may explain some of the discrepancies regarding Brent's year of birth, life, and activities during the 1919 to 1922 period.

He appeared in productions of Abie's Irish Rose (on tour for two years), Stella Dallas, Up in Mabel's Room, Elmer the Great, Seventh Heaven, White Cargo and Lilac Time.

He acted in stock companies at Elitch Theatre, in Denver, Colorado (1929), as well as Rhode Island, Florida, and Massachusetts.

Brent appeared in The Rich Are Always with Us (1932) with Ruth Chatterton (who became his second wife that year), in which Davis again had a supporting role.

In October 1933, he and Chatterton refused to make a film they had been assigned, Mandalay, and were replaced by Lyle Talbot and Kay Francis.

[15] He was top-billed in From Headquarters (1933) with Margaret Lindsay; Metro-Goldwyn-Mayer borrowed him to play Myrna Loy's leading man in Stamboul Quest (1934).

Brent appeared in The Goose and the Gander (1935) with Kay Francis, then was borrowed by RKO to make In Person (1935) with Ginger Rogers.

At Warners he was top billed in the comedy Snowed Under (1936), then Walter Wanger borrowed him to play Madeleine Carroll's leading man in The Case Against Mrs. Ames (1936).

Columbia borrowed him to support Jean Arthur in More Than a Secretary (1936) then Warners gave him top billing in God's Country and the Woman (1936) with Margaret Lindsay.

Warners put him in an action "B" film with Humphrey Bogart, Racket Busters (1938) then he was reunited with Francis in Secrets of an Actress (1938).

[20] Columbia borrowed him for the lead role in They Dare Not Love (1941) with Martha Scott and Edward Small used him in two films, International Lady (1941) with Ilona Massey and Twin Beds (1942) with Joan Bennett.

He supported Stanwyck in The Gay Sisters (1942) and was top-billed in You Can't Escape Forever (1942) with Brenda Marshall and Silver Queen (1942) with Priscilla Lane.

[24] While Brent returned to his acting career after WWII, he never recaptured his former popularity but during the immediate post war period he still remained a star of big budget films.

For Hal Wallis he did The Affairs of Susan (1945) with Joan Fontaine then Tomorrow Is Forever (1946) at International with Claudette Colbert and Orson Welles.

At Universal he was teamed with Lucille Ball in Lover Come Back (1946), then he made Temptation (1946) with Oberon and Edward Small at International.

[28] Brent was married five times: to Helen Louise Campbell (1925–1927), Ruth Chatterton (1932–1934), Constance Worth (1937),[29] Ann Sheridan (1942–1943), and Janet Michaels (1947–1974).