Belinda Fewings, 69, from Bournemouth, was walking with her husband and their two Greek rescue dogs when they spotted the actor filming on the beach.
She said: “We stopped about 50 yards away from all the activity when we spotted Ben Stiller, who had ‘Vince’ printed on his top.
“As we were watching, we were surprised when he and his assistant came over to say hello to us and our little dogs.”
Mrs Fewings said her husband asked Stiller what he was doing on the beach, and the actor replied that he was filming scenes for a movie.
She added: “He was really very pleasant and was smiling down at our dogs.
“We didn’t want to ask too much because he had a script in his hand.
“We all smiled, said ‘have a nice day’ and turned back as the beach was gradually being closed.
“I was so surprised to see such a big Hollywood star down on the beach.
“It certainly made our day.”