Susan Schneider said her husband, who had spoken openly of his struggles with drug and alcohol addictions, had been sober but "not yet ready to share publicly" his struggles with the neurological condition.
Robin Williams's friend, the Scots comedian Billy Connolly, was diagnosed with the disease last year.
Ms Schneider added that her husband had also been suffering from anxiety and depression. The 63-year-old Mrs Doubtfire actor was found dead in his San Francisco home on Monday.
She added among his greatest legacy was the joy and happiness he gave to others, particularly those fighting personal battles.
Ms Schnieder added: "It is our hope in the wake of Robin's tragic passing, that others will find the strength to seek the care and support they need to treat whatever battles they are facing."