Dariush began training Brazilian jiu-jitsu in 2007, earning his black belt in just five years. He was a highly decorated competitor, becoming a no gi world champion as a blue, purple and brown belt. Dariush made his professional MMA debut in November 2009. During the first three and a half years of his career, he went undefeated with six wins and no losses. He finished all but one of those wins.
Dariush made his PPV debut at UFC 179 on October 25, 2014, defeating the undefeated Carlos Diego Ferreira by unanimous decision.
Dariush next faced Michael Johnson on August 8, 2015 at UFC Fight Night 73. Dariush won the fight via controversial split decision. Every mainstream MMA media outlet scored the fight as a decision victory for Johnson.
Dariush faced Rashid Magomedov on November 5, 2016 at The Ultimate Fighter Latin America 3 Finale., He won the fight via unanimous decision.
Dariush fought Evan Dunham on October 7, 2017 at UFC 216. The fight ended in a majority draw, with one judge scoring the bout for Dariush.
Dariush was expected to face Bobby Green on March 3, 2018 at UFC 222. However, on February 14, 2018, it was announced that Green was forced to pull out from the event, citing injury. Green was replaced by Alexander Hernandez. Dariush lost the fight via knockout in the first round.