As far as we know at present, she doesn't have a boyfriend. There has been speculation about her love life ever since her split from Tom Cruise, but nothing has been confirmed yet.
Recently it was thought she was seeing a new man, but it turned out to be her one-time boyfriend and former co-star on Dawsons Creek, Joshua Jackson. Of course it is always possible that there could be an announcement ... But so far they just seem to be friends (they had no more contact after her marriage to Cruise).
Lately Katie Holmes has said that she is going to be very careful about dating from now on. For one thing, she says she would prefer to avoid men more than a few years older than her - Cruise was 17 years her senior and this may have been one cause of the breakdown in their relationship.
You can read more about this here.