The 38-year-old performer, who won a 2005 Grammy Award for his hit You'll Think of Me, did not disclose the location of the centre or the nature of his treatment.
In the past he has acknowledged struggles with cocaine and alcohol..
"I deeply regret the hurt this has caused Nicole and the ones that love and support me, the singer said in a statement released through his publicist.
"One can never let one's guard down on recovery and I'm afraid that I have," Urban said in the statement.
"With the strength and unwavering support I am blessed to have from my wife, family and friends, I am determined and resolved to a positive outcome."
On his web site, the New Zealand-born country superstar told fans that he was "calm and optimistic about the future and finally coming to terms with the reality of my condition."
Publicist Paul Freundlich said that because of the treatment Urban would suspend appearances for the release of his CD Love, Pain & The Whole Crazy Thing, which is scheduled to hit stores on November 7.