Ford returned to City Hall on July 1 after completing two months in rehab for substance abuse.
He previously said in a handful of interviews that he couldn't guarantee he will remain sober, only that he's taking his recovery one day at a time.
But on Thursday he said, "A lot of people really wish that I'm going to fail, that I'm going to drink and that I'm going to do drugs. Unfortunately, that wish will not come true."
Ford's time in office has been marred by revelations about his substance abuse and erratic behavior. Toronto's City Council stripped Ford of most of his powers last year. He's running for re-election.