He is perhaps best-known as Mr. Potter's silent, wheelchair-pushing valet in Frank Capra's classic It's a Wonderful Life (1946).

Hagney was also a guest star on more than 70 television programs such as The Cisco Kid, The Adventures of Kit Carson, The Lone Ranger, The Rifleman, Perry Mason, and Daniel Boone.

In 1956 he appeared as a Townsman in an uncredited role in the TV western Cheyenne in the episode titled "The Last Train West."

He starred in The Fighting Marine (1926) with Jack Anthony, Joe Bonomo and Walter Miller; The Fighting Sap (1924) with Bob Fleming, Hazel Keener, Wilfred Lucas and Fred Thomson;[2] The Ghost in the Garret (1921), Ghost Town Gold (1936), Go Get 'Em Hutch (1922) with Richard R. Neil;[3] Ride Him Cowboy (1932) with Eddie Gribbon and John Wayne, Valley of the Lawless (1936), and Vultures of the Sea (1928) with Joseph Bennett.

[5] His 54 sound western film included The Phantom of the West (1931), Fighting Caravans (1931), The Squaw Man (1931), The Golden West (1932), Honor of the Range (1934), Western Frontier, Heroes of the Range (1936), Billy the Kid, The Lone Rider Rides On (1941), Blazing Frontier (1943) and The Wistful Widow of Wagon Gap (1947).