The 44-year-old star announced the news on his Facebook page via his representative.
"Earlier today, with the support of his professional team, his friends, and his family, Nicky entered a rehabilitation facility in California to treat his depression, alcoholism, and substance abuse problems. He's taking the steps necessary to better his health and give himself, and his fans, the gift of a healthy lifestyle," the post read.
"Nicky will not be attending any events during the months of June and July- but has plans to return to the circuit in late summer after he has successfully completed his treatment program."
"Nicholas is excited for the opportunity that comes with recovery," his manager told The Hollywood Reporter in a statement.
"He knows it will be a long and difficult road, but he's happy that he's receiving the help he needs. We support him 100 per cent.