The filmmaker says he has "indelible" memories attached with the movie, while its lead actor Shah Rukh Khan missed the film's producer, late Yash Johar on the occasion.
The movie, which featured Shah Rukh, Saif Ali Khan, Preity Zinta and Jaya Bachchan in key roles, released Nov 28, 2003.
"'Kal Ho Naa Ho' completes a decade... Har pal yahaan jee bhar jeeyo, jo hai samaa, kal ho naa ho...indelible memories," Karan posted on Twitter.
The film marked the directorial debut of Nikhil Advani, who posted: "'Kal Ho Naa Ho' is 10 years old…Thanks to Karan Johar, Shah Rukh Khan and Yash (Johar) uncle. They were the ones who gave me the chance. Everything else came later."
Shah Rukh, who played the endearing character of Aman Mathur in the film, thanked "the whole team" of the film, especially "Yash Johar (Tom uncle)...you were most special. Miss you."
"Kal Ho Naa Ho" was Yash Johar's last production venture before he died June 29, 2004.