The 62 year-old comedian has not relapsed, but just wants to "fine-tune and focus on his continued commitment" to maintaining sober.
Robin Williams recently entered rehab once again, but it is only a precaution.
The comedian hasn't had any setbacks or fallen off the wagon, he just wants to attempt to maintain his sobriety.
TMZ reports, Williams checked into the Hazelden Addiction Treatment Center in Minnesota.
"After working back-to-back projects, Robin is simply taking the opportunity to fine-tune and focus on his continued commitment, of which he remains extremely proud," the 62 year-old's rep said in a statement.
Williams is reportedly in a program called The Lodge, which the rehabilitation center's website describes as "immers(ing) you in the Twelve Step design for living that can inform and transform every aspect of your life."
TMZ also notes that the 'Mrs Doubtfire' actor will be staying at the facility for several weeks.
This wasn't a spontaneous decision either, a source close to him told E!News, "This was totally planned and scheduled, He's been working for about 18 months straight. He had some time off so is using it to do a check-in."
Most recently Williams was starring alongside Jennifer Love Hewitt in the CBS series 'The Crazy Ones' as Simon Roberts, an eccentric Chicago advertising executive, but the television network chose to cancel it after one season.
The funnyman has always been very open about his past struggles with drugs and alcohol abuse, but after being sober for 20 years he relapsed while filming the 2005 movie 'The Big White.' A year later he entered rehab and has been clean ever since.
"One day I walked into a store and saw a little bottle of Jack Daniel's. And then that voice-I call it the 'lower power'-goes, 'Hey. Just a taste. Just one,'" Williams said to Parade about falling off the wagon in 2005. "I drank it, and there was that brief moment of 'Oh, I'm okay!' But it escalated so quickly."
Adding, "Within a week I was buying so many bottles I sounded like a wind chime walking down the street. I knew it was really bad one Thanksgiving when I was so drunk they had to take me upstairs."
Williams will stay in the rehabilitation facility for several weeks