"Nine years to 'Kal Ho Naa Ho'... the last film my father helmed at Dharma Productions. An ironic title of a very special film to me... always," Karan tweeted.
The movie released on Nov 28, 2003.
Nikhil Advani, who made his debut as a director with "Kal Ho Naa Ho", also thanked Karan for "giving" him a "dream start".
"Thank you for giving me the dream start!!!" tweeted Advani.