Stone-cold sober actress Kim Delaney was so determined to stay on the wagon that she checked into a rehab clinic to prevent herself from boozing.

That’s the REAL story behind the shocking news that the “NYPD Blue” star — who was arrested for driving under the influence last year — entered Sierra Tucson, an Arizona substance abuse treatment center.

“I am very proud of Kim and her decision to take control of her life,” her father Jack Delaney told The ENQUIRER.

“She’s been sober for several months now and I assure you she was not drinking prior to entering rehab. It was a decision to prevent a relapse — not because of one.”

A series of stressful events prompted Kim, 41, to seek help, he said.

“Kim’s engagement to her longtime fiancé was broken off. She left ‘CSI: Miami’ and I became very ill with cancer — at the same time.

“It was just too much for her.

“Besides that, Kim is a perfectionist. She believes in working hard, but she also wants to be the best mother in the world to my grandson, Jack. And there are only so many hours in a day.

“For a while there, the stress took a toll. But now Kim’s back on the right track.”

Kim’s biggest worry was her father’s diagnosis of prostate cancer.

“Jack was diagnosed a little over a year ago,” a family friend told The ENQUIRER.

“Kim was absolutely devastated. She’s the only girl out of six children — and extremely close to her father.

“For almost a year, she lived with the anguish of thinking her father may die.

She even brought her parents from Philadelphia to Los Angeles to live with her.

“Meanwhile, David Caruso made life on the set of ‘CSI: Miami’ a living hell. He’s a control freak who’s not happy unless everyone else is unhappy.

“Kim spent many nights crying alone because she didn’t want anyone to know how difficult her situation was.

“Now instead of hiding her pain and taking a drink, she’s learned to reach out for help. That’s why she’s in rehab.

“If all goes well, Kim expects to be home by Memorial Day.

“And her father has been told his cancer is gone.

“So for the first time in a long time, most of Kim’s worries are behind her.”