Born in Lawrence, Kansas, he graduated from Ohio State University and then attended the prestigious Yale School of Drama, where he appeared in productions of "The Vultures", "We Can't Pay, We Won't Play", and "Las Madres".
His television debut was in V: The Series as Kyle Bates. Later, he starred in the pilot of 21 Jump Street as Tommy Hanson, the role that was taken over by Johnny Depp. He also appeared in several episodes of Six Feet Under, playing Hoyt Woodworth, in 2004. Most recently, Jeffrey continues to appear in other shows such as Without a Trace (2007) and Bones (2009).
Additionally, Yagher was an Elvis impersonator in an episode of The Twilght Zone called The Once And Future King. (The man who played Elvis' boss at the Crown Electric company was Red West, a real-life schoolmate and best friend of Elvis'.)
His feature film credits include My Fellow Americans, Shag, The Pandora Project, and View from the Top.
He also appeared in an episode of Newhart as Stoney.
He starred in the TV movie Bionic Showdown: The Six Million Dollar Man and the Bionic Woman along with Sandra Bullock in 1989.
He also appeared in an episode of Seinfeld as a Jazz musician who dated Elaine.