The Don 2 star, whose time in films began 20 years ago yesterday (June 25), claimed he just "got lucky".
Sharing his thoughts about the milestone on Twitter, he said: "Twenty uninterrupted years of serving. Not enough talent or looks or game plan... I guess I got lucky, lucky to be working all the time.
"Made mistakes, still continue to do so. A little madness, a bit of solitude. Too silly to realise it's impossible & maybe that's why it gets achieved."
The 46-year-old star also paid tribute to his parents, saying: "Mum said to only feel & say positive things. Your Farishtey (angels) are always listening & fulfilling your words. My Farishtey work overtime."
Khan, who is currently in London shooting for an as-yet-untitled Yash Raj film, marked 20 years in Bollywood by presenting his own live radio show on BBC Asian Network on Thursday (June 21).
The actor, who launched his career with the film Deewana in 1992, has since starred in over 70 movies and is today regarded as the biggest superstar of Indian cinema.