Tomko, who turns 36 on April 7, split last season between the Kansas City Royals and San Diego Padres.
He was 2-7 with a 6.30 ERA in 22 combined games (10 starts). Tomko began the campaign with Kansas City before being released on June 20. Tomko signed with San Diego a week later but was released again on Sept. 1.
In his 12 Major League seasons, Tomko has compiled a record of 95-99 and a 4.68 ERA in 368 games (260 starts) with the Cincinnati Reds, Seattle Mariners, Padres, St. Louis Cardinals, San Francisco Giants, Los Angeles Dodgers and Royals.
"Brett is a guy that can do a lot of different things," Yankees manager Joe Girardi said. "He can start, he can relieve, he can long relieve or [be a short guy]. He's a guy with a good arm and we just felt we wanted him for depth. One thing that you want to have on this club is a long reliever or spot starter."
Yankees general manager Brian Cashman has been searching for additional free agents who are willing to accept non-roster invitations to big league camp and compete for potential jobs. Tomko will wear uniform No. 53, last worn by outfielder Bobby Abreu.
The addition brings the number of players expected in camp to 64. Yankees pitchers and catchers reported to George M. Steinbrenner Field on Friday.
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.