According to promotion officials, Leben tested positive for Oxycodone and Oxymorphone following his main event loss to Mark Munoz. The suspension was handed down on late Monday afternoon.
"I like Chris and I want him to do well, but based on his actions, he's been suspended for one year," UFC President Dana White said. "If he needs professional help, we are going to be there for him. We want to see him succeed not only in the Octagon, but in his personal life."
Previously, Leben received a nine-month suspension in 2008 after testing positive for Stanozolol following a unanimous decision loss to Michael Bisping at UFC 89.
"I would like to make it known that I fully accept this suspension and apologize for embarrassing the UFC, my friends and family, and sport of mixed martial arts," Leben said.
"I'm learning that I'm my own worst enemy sometimes. I can't succeed in the Octagon or in life behaving this way. I've got to make some real changes over the next year and I'm going to focus on getting my life and career back on track. Again, I'm sorry to the UFC and fans that've supported me since my days on The Ultimate Fighter."