Born in Westchester County, New York, the actor trained at NYU and acted on stage in several productions, including "Yerma" and "Into the Woods". Not long after earning his BA, Maher got what should have been his first big break, the lead role in a Fox drama about a rookie cop. A troubled pre-production period (during which the show's title was changed from "The Badland" to "Ryan Caulfield: Year One") and a rather unbelievable premise (Caulfield is an 18-year-old rookie!) torpedoed the series and its dismal ratings coupled with critical brickbats led to an early cancellation after only two episodes. In spite of the reviewer's carpings about the storyline, though, Maher received generally favorable reviews for his work.
He bounced back landing a recurring role as the final love interest for Neve Campbell's Julia Salenger on Fox's "Party of Five" in 2000. The charismatic performer then joined his former co-star's brother Christian Campbell in the ensemble of the Darren Star-created drama "The $treet" (Fox, 2000). Here he was cast as a former Navy SEAL from a working-class background now making a living and enjoying the fast-line lifestyle of a Wall Street trader. After the show's quick demise, he was cast in the ABC/Disney remake of "Brian's Song" (2001), playing cancer-stricken football player Brian Piccolo.
Hoping for a more stable primetime presence, Mahar next signed on as a member of the crew of the futuristic spaceship Serenity on the sci-fi pilot "Firefly," from "Buffy the Vampire Slayer" creator Whedon. Mishandled by Fox, the series had only a brief run before the network pulled the plug, but it garnered a rabid core of loyal fans. DVD sales of the series were brisk, and Whedon was able to revive the franchise for the feature film "Serenity" (2005), in which Maher reprised his role as Simon, who was crucial to the film's plotline. In between Maher guest starred on such series as "CSI: Miami" and "Ghost Whisperer," and appeared in the lead in indie writer-director's Amanda Goodwin's film "Living 'Til the End" (2005), playing a man who, after being told by a psychic of his imminent death on his next birthday, lives out the year as a hopeless agoraphobic until he meets a young woman who slowly coaxes him out of his self imposed bondage.