"Tapan Sikdar ji's demise is extremely saddening. May his soul rest in peace," Modi said in a tweet.
He added: "Tapan Sikdar will be remembered for his rich contribution in building the BJP and his years of dedicated public service."
Sikdar was a union minister in the Atal Bihari Vajapyee government from 1999 to 2004.
He was admitted to the All India Institute of Medical Sciences (AIIMS) here May 29.