Karan made his directorial debut with the romantic comedy drama, which starred Shah Rukh, Kajol and Rani Mukerji. "Kuch Kuch Hota Hai", which released on October 16, 1998, also had a cameo by superstar Salman Khan.
"18 years of 'Kuch Kuch Hota Hai'. The film that will always remain close to my heart. Shah Rukh Khan and Adi (Aditya Chopra) made my cinema dream come true," Karan tweeted on Sunday.
"Kuch Kuch Hota Hai" was distributed by Aditya Chopra's home banner Yash Raj Films.
It also featured Sana Saeed, Farida Jalal and Anupam Kher.