Yelchin was born in Leningrad, USSR (now Saint Petersburg, Russian Federation), the son of Irina Korina and Viktor Yelchin, figure skaters who were national celebrities as stars of the Leningrad Ice Ballet for fifteen years. Yelchin's parents qualified for the 1972 Winter Olympics, but because they were Jewish, were not permitted to participate by the Soviet authorities. Yelchin's family moved to the United States in September of 1989, receiving status as refugees from political and religious oppression. Yelchin's mother now works as a figure skating choreographer and his father as a figure skating coach, having been Sasha Cohen's first trainer. Yelchin's uncle is painter Eugene Yelchin.

Yelchin enjoys playing the guitar, saying that it gives him "a lot of fulfillment", and is a fan of acoustic blues music. He attended the Sherman Oaks Center for Enriched Studies, in Tarzana, California, and enrolled at the University of Southern California in the fall of 2007 to study film.

Yelchin began acting at the age of nine, in the independent film A Man is Mostly Water. His earliest roles include Jackson in A Time for Dancing, Milo in Delivering Milo, Tommy Warshaw in House of D, and "Jacob Clarke" in the mini-series Taken. He made a guest appearance as Stewart, Cheryl David's nephew and a self-described magician (who only knows one card trick), in a season four episode of Curb Your Enthusiasm, and starred as Byrd Huffstodt, the fourteen year-old son of Dr. Craig "Huff" Huffstodt (Hank Azaria on the television series Huff, which ran from 2004 to 2006. In 2006, he also had a role on an episode ("Tru Love") of the series Law & Order: Criminal Intent, playing the son of a dead doctor. His biggest film recognition came for the role of Bobby Garfield in Hearts in Atlantis (2001), for which he won Best Performance in a Feature Film - Leading Young Actor at the 2002 Young Artist Awards. He also appeared as Nathan Harris in Criminal Minds' episode "Sex, Birth & Death".

In 2007, Yelchin starred in Alpha Dog, a crime thriller that received a U.S. release on January 12. In the film, he played Zack Mazursky, who is based on real-life kidnap and murder victim Nicholas Markowitz. USA Today's review described the performance as "heartbreakingly endearing". Yelchin felt awkward appearing in the swimming pool-set sexual scene in the film, specifying that he felt "uncomfortable" for his co-stars and that he could not "imagine enjoying it or taking pleasure" in filming the scene.Fierce People, a drama co-starring Yelchin, Diane Lane and Donald Sutherland, received a limited release on September 7 of that year. Charlie Bartlett, in which Yelchin plays the title role of a wealthy teenager in a public high school, was released on February 22, 2008. He will next appear in You and I, which was filmed in Moscow during the summer of 2007, Middle of Nowhere, opposite Susan Sarandonand Justin Chatwin, and the eleventh Star Trek film, in which he will portray Pavel Chekov. In February 2008, he was cast as a teenage Kyle Reese in Terminator 4.