Urban has been in the in-patient rehabilitation program since he checked himself into the center on Oct. 19, Us Magazine reported Monday.
The following day, Urban received the best male vocalist honor at the Country Music Association Awards.
His good friend Ronnie Dunn, of Brooks & Dunn, read a letter from Urban in which he thanked his friends and family, stating "I'm pained not being there with y'all tonight," and "To my wife, Nicole, I love you."
Urban is expected to be at the center for 35 to 40 days.
This is the second stint in rehab for the country singer. In 1998, he checked into the Cumberland Heights treatment center in Nashville, Tenn., for treatment of cocaine and alcohol addiction.