Jones (21-1) successfully defended his belt for the eighth consecutive time Saturday night at MGM Grand in Las Vegas, defeating previously unbeaten Daniel Cormier by unanimous decision.
Jones was found through a random test by the Nevada State Athletic Commission on Dec. 4 to have benzoylecgonine, a cocaine metabolite, in his system. The street drug does not prevent athletes from competition, however, and a followup test reportedly came back clean.
"With the support of my family, I have entered into a drug treatment facility," Jones said in a statement to Yahoo! Sports. "I want to apologize to my fiancee, my children, as well as my mother, father and brothers for the mistake that I made.
"I am taking this treatment program very seriously."
The UFC, aiming to have Jones fight the winner of the Jan. 24 Alexander Gustaffson-Anthony Johnson fight in July, did not express an interest in disciplining Jones for the positive test.
It released a statement saying: "We support Jon Jones' decision … to address his recent issue. While we are disappointed in the failed test, we applaud him for making this decision to enter a drug treatment facility. Jon is a strong, courageous fighter inside the octagon, and we expect him to fight this issue with the same poise and diligence. We commend him on his decision, and look forward to him emerging from this program a better man as a result."
It's not clear when the UFC learned of Jones' positive cocaine test result. Requests by the Los Angeles Times to speak to Chairman Lorenzo Fertitta and UFC President Dana White were denied; a company official said the UFC's statement was the extent of the organization's comment.
White said in a prepared statement: "I am proud of Jon Jones for making the decision to enter a drug treatment facility. I'm confident that he'll emerge from this program like the champion he truly is."
Jones has won 12 consecutive fights and spoke after his victory on Saturday of surpassing former champions Anderson Silva and Georges St-Pierre as the greatest UFC fighter in history.
"It's so feasible and attainable," said Jones, now two victories behind Silva's record 10 straight successful title defenses. "I do believe 2015 will be the year I solidify that."