Palhares, who suffered a first-round knockout loss to Hector Lombard, was flagged for an elevated testosterone level.
Beltran tested positive for the steroid nandrolone. His decision win over Igor Pokrajac will be changed to a no-contest.
The event took place on Dec. 15 in Queensland, Australia. The suspensions are dated retroactively to Dec. 14, the day in which the card aired in the U.S.
International drug testing is typically conducted by the UFC, when no regulatory body is present. Vice President of Regulatory Affairs Marc Ratner, a former member of the Nevada State Athletic Commission, oversees the process.
Palhares (14-5) holds seven wins in the UFC, but is currently on a two-fight losing streak. The Brazilian middleweight has had several strange occurrences in his career, including a 90-day suspension by the New Jersey State Control Board for failing to release a submission after opponent Tomasz Drwal tapped.
A former heavyweight, Beltran (15-8) dropped to 205 pounds this year. The San Diego-based fighter accepted his suspension but stated via Twitter on Thursday he was still searching the cause for the positive test.
"I can say without a shad or a doubt I did no inject nandrolone into my body," Beltran tweeted. "I am sorry to my family and friends for the shame this brought to any of you."