The 64-year-old actor starred opposite the late actress - who passed away in 2009 after a skiing accident - in the 1988 remake of 'The Parent Trap' and he will always remember her as a ''beautiful'' person.
He said: ''Now you hit my heart. She was such a beautiful person, such a beautiful, beautiful person. Just none of that, that actor stuff, prima donna stuff.
''Someone easy to work with and such a great sense of humour.''
And Dennis recalled how the passing of Natasha - who was married to Liam Neeson, the father of her sons Michael and Daniel - hit everyone who knew her very hard.
He added in an interview with Us Weekly magazine: ''When that accident happened, it just devastated me and so many other people.
''She had such a beautiful love, married life with Liam, and two beautiful boys. She always had a smile on her face when she came to work. That really affected everyone around her.''
Dennis is proud that 'The Parent Trap' - which starred Lindsay Lohan as twin girls conspiring to get their divorced parents back together - has remained so popular and joked it was used as a ''babysitter'' to keep children occupied in the late 1980s.
He said: ''Things start to go by so quick. That movie just keeps going on and on and on.
''You know, the first one was made with Hayley Mills. I think I was about 10 years old when I saw it. Brian Keith played the dad in that. Hayley Mills, oh my gosh, I had such a crush on her.
''But, 'The Parent Trap' was made during the time of VHS. When it came out on VHS I think every parent in America used it as a babysitter while they were at home. So many kids saw that like 40 or 50 times.
''I usually say, 'Yeah, I used to be a babysitter while your parents were doing what they wanted to do.'''