"The support and words of encouragement I have received over the past few weeks certainly help to support my efforts in recovery which I take seriously every day," Kennedy said in a statement.
The congressman, who has struggled with depression, alcoholism and addiction for much of his life, checked into the Father Martin's Ashley in Havre de Grace, Md., last month. The son of Sen. Edward Kennedy, D-Mass., has called his treatment "a lifelong process."
The congressman spent the July 4 weekend on Cape Cod visiting his father, who is battling brain cancer.
Kennedy previously sought treatment after an early morning car crash near the Capitol three years ago.