Toub, who is of Persian Jewish background, was born in Tehran, Iran and raised in Manchester, England (his family left Iran before the 1979 revolution). At the age of fourteen, he moved to Switzerland and after a two year stay, he crossed the Atlantic to Nashua, New Hampshire to finish his last year of high school. His high school yearbook notes: "The Funniest guy in school and the most likely to succeed in the entertainment world." After two years of college in Massachusetts, Shaun transferred to University of Southern California.
Shaun is active in the Iranian Jewish community. Through various charity events and public speaking engagements, he inspires the community to embrace the arts. He has been a recipient of the Sephard award at the Los Angeles Sephardic Film Festival. Toub currently resides in Los Angeles.
Toub broke into the Hollywood scene, through a chance encounter with an astute talent agent. He has received accolades for several of his appearances in over one hundred television episodes including Seinfeld, the Sopranos, ER, Just Shoot Me, Sliders, Nash Bridges, JAG, The Bold and the Beautiful, Lois & Clark: The New Adventures of Superman, Married... with Children, Lost, and various movies made for television.
His filmography includes his memorable performance in Michael Bay's Bad Boys with Will Smith and Martin Lawrence, John Woo's Broken Arrow with John Travolta and Christian Slater, Mick Jackson's Live from Baghdad and Path to Paradise. His performance as Farhad in Paul Haggis's Oscar-winning film Crash, a critical and box office surprise hit, received positive reviews. He also plays the role of Rahim Khan in The Kite Runner (2007).
He appeared in the Marvel Comics adaptation Iron Man as Yinsen.