Zak, 31, said that he misses him all the time, reported People magazine.
"Often I see something or if I'm watching a film, I think, 'Oh, man, he would have appreciated this' or 'He would have gotten a laugh out of this'," he said.
Talking about himself and his siblings Zelda and Cody, Zak said, "There's not a day that goes by that we don't think about our dad."
The eldest son of Robin Williams and Valerie Velardi has been volunteering at a local prison to honour the late actor's spirit of giving back.
Robin passed away on August 11 after hanging himself with a belt. His wife said that he was battling early stage of Parkinson's disease before committing suicide.
