The singer's spokesperson told People that Rimes entered an in-patient medical centre on Wednesday (August 29), but stressed she is not being treated for substance abuse or an eating disorder.
Her representative said: "LeAnn has voluntarily entered a 30-day in-patient treatment facility to cope with anxiety and stress.
"While there will be speculation regarding her treatment, she is simply there to learn and develop coping mechanisms. While privacy isn't expected, it's certainly appreciated."
Rimes also offered her own explanation for entering a treatment facility, saying that she needs time to "take care of herself".
"All the things in my life will be there when I get out, but you know what? I'm hoping they're not going to affect me as much," she explained. "I'll have the tools to know how to deal with them."
Rimes is expected to honour all September concerts dates during brief breaks from her treatment. She is next scheduled to perform in Eau Claire, WI on September 7.
Her husband Eddie Cibrian offered his support to Rimes by praising her for "having the strength to finally take some time for herself".
Cibrian and Rimes married in April 2011 at a friend's private home in California.