The Microsoft founder, 65, first met Epstein in 2011 after the financier had been convicted of soliciting sex from a minor in 2008.
Epstein was also invited to fundraising dinners that promoted the Gates Foundation.
'At the time, I didn't realize that by having those meetings it would be seen as giving him credibility,' Gates told The Times in an interview Sunday.
'You're almost saying, 'I forgive that type of behavior,' or something. So clearly the way it's seen, I made a huge mistake not understanding that.'