Born and raised in Little Rock, Arkansas, Newbern began acting a child in community theater productions. By age 14, he had won a scholarship to the Minneapolis Children's Theater, where he worked for several summers. During his senior year in high school, Newbern landed his first TV role, a bit part as a Union soldier who deserts, in the CBS miniseries "The Blue and the Gray" (1982). He attended Northwestern University (where he met his future wife, actress Marietta DePrima) and spent a summer at RADA. After graduating, he moved to L.A. to pursue an acting career.
Almost immediately, Newbern landed the occasional role of Payne, the son of Julia Sugarbaker (Dixie Carter) on the CBS sitcom "Designing Women". He went on to star as twins opposite Elisabeth Shue in the TV-movie "Double Switch" (ABC, 1987) landed a regular berth as the yuppie co-worker of Sandra Bullock's "Working Girl" (NBC, 1990). In 1994, Newbern was one of the sons of Hal Linden and Suzanne Pleshette who move in with the folks in the short-lived CBS sitcom "The Boys Are Back". Other credits include "Poochinski" (NBC, 1990), "Judith Krantz's 'Torch Song'" (ABC, 1993), and playing Robert Culp's son in "I Spy Returns" (CBS, 1994).
At the same time, Newbern was keeping busy in films, He debuted in supporting roles in the teen films "My Little Girl" and "Adventures in Babysitting" (both 1987). In the latter, he was reteamed with Elisabeth Shue as a college student who comes to her rescue. After another supporting role, as a wise-cracking valet, in the weak comedy "Switching Channels" (1988), Newbern began landing leading roles in the comedies "It Takes Two" and "Paramedics" (both 1988).
But his first real notice came with "Father of the Bride" (1991), as Kimberly Williams' fiance and the prospective son-in-law of Steve Martin and Diane Keaton. He reprised the role in the imaginatively-titled "Father of the Bride Part II" in 1995. The following year, he had the meaty role as the drug-dealing grandson of Aurora Greenway (Shirley MacLaine) in Robert Harling's "The Evening Star" and was a gay man visiting with friends in the satirical comedy "Far Harbor/Mr. Spreckman's Boat".
Newbern and Kimberly Williams were also teamed in a series of TV commercials for Hallmark greeting cards that played off their screen roles as newlyweds.