The Rhode Island Democrat said in a statement that his recovery is a "lifelong process" and that he will do whatever it takes to preserve his health.
"I have decided to temporarily step away from my normal routine to ensure that I am being as vigilant as possible in my recovery," Kennedy said. He did not disclose where he was being treated.
Kennedy, who has wrestled with alcoholism, bipolar disorder, an addiction to prescription drugs and bouts of binge drinking, has often spoken publicly about his recovery and the importance of removing any stigma associated with mental illnesses. He has been a leading voice in Congress on mental health issues.
"I hope that in some small way my decision to be proactive and public in my efforts to remain healthy can help remove the stigma that has served as a barrier for many Americans reluctant to get the help they needed," he said.
Kennedy's office declined to offer any details about the congressman's health or what prompted him to seek treatment. He sought the treatment in the last few days, his office said.
In May 2006, Kennedy, the son of Sen. Edward Kennedy, D-Mass., crashed his 1997 Ford Mustang into a security barrier on Capitol Hill in the early morning hours. He entered into a rehabilitation program at the Mayo Clinic in Minnesota. He agreed to a plea deal on a charge of driving under the influence of prescription drugs and received a year's probation.
The congressman's latest treatment comes as his 77-year-old father is battling brain cancer.