Urban released a statement Friday that said he entered rehab Thursday night with his wife by his side. His publicist would not give the location of the rehab center.
"I deeply regret the hurt this has caused Nicole and the ones that love and support me," Urban said in the statement.
Urban, who turns 39 on Oct. 26, has publicly acknowledged a former addiction to cocaine, but his publicist said Urban was currently being treated for alcohol abuse.
"One can never let one's guard down on recovery, and I'm afraid that I have," the statement reads. "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."
His new CD, "Love, Pain, & the whole crazy thing," will be released Nov. 7 as scheduled, but he will postpone all upcoming promotional appearances.
Urban will also likely cancel a scheduled appearance on the Country Music Association awards next month, the publicist said.
Kidman and Urban, both of whom were raised in Australia, married on June 25 in Sydney. They then moved to Nashville, where Urban records.
Urban won a Grammy this year for best male country vocalist for "You'll Think of Me," and was named top male vocalist for the second year in a row by the Academy of Country Music.
A Country Weekly magazine reader poll this year named him country music's sexiest man.