Born in El Toro, California to Alice and Jeff Krause, he is the younger of their two children. His older brother is named Patrick. Brian grew up in Southern California and took his first acting class with R. J. Adams at The Actors Workshop while in junior high as a way to avoid a bully in physical education class. In his teens, he studied karate, and attended El Toro High School, graduating in 1987. He continued his education at Orange Coast College where he played and lettered in soccer, scoring four goals as a midfielder and forward. He later then had a child.
Krause landed his first role in 1989 as a student in the TV series TV 101. He then starred in the made-for-TV-movie Match Point, the CBS Schoolbreak Special "American Eyes", and An American Summer, before landing his first major role as Richard Lestrange in Return to the Blue Lagoon. He was a co-star in the Bandit series prior to his most notable role of Leo in The WB Network series Charmed (1998–2006). Krause originally auditioned for the role of Andy Trudeau, but was cast as Piper's handyman love interest, Leo Wyatt. Due to budget restrictions in the eighth season (2005–06), he only appeared in the first 10 episodes, and in the last two episodes. After Charmed, he has appeared in made-for-TV-movies and TV shows such as Mad Men and The Closer. He has portrayed a minor character (Clem Feeney) in the videogame L.A. Noire, lending his voice and image to it. He also appeared on the YouTube video series Chad Vader, specifically "Season 4 Episode 4: The Return of Brian" as himself, a former employee of Empire Market. The video was uploaded 10 July 2012