Patnaik, 89, passed away at a private hospital at 3 a.m on April 20, 2015.
Patnaik had arrived at Tirupati to attend the convocation of Tirupati Rashtriya Sanskruta University as the chief guest.
Patnaik was the university’s chancellor.
Later, he was admitted in a hospital after he complained of severe chest pain, said Soumya Ranjan Patnaik, the former chief minister’s son-in-law.
Patnaik, a veteran Congress leader, is survived by his wife Jayanti Patnaik, son Pruthvi Ballav Patnaik and two daughters — Sudatta Patnaik and Supriya Patnaik.
The mortal remains of the late leader will be flown to Bhubaneswar by a special flight in the afternoon for cremation at Swargadwara in Puri.
Patnaik had returned to Odisha in December last year after serving as governor of Assam.
He was born at Rameswar village in Khordha district on January 3, 1927.
He was the chief minister of Odisha for two terms – from 1980 to 1989 and from 1995 to 1999 and from He was also the leader of opposition in Odisha assembly from 2004 to 2009.
The veteran Congress leader was also an eminent litterateur and journalist and has written several books.
As a mark of respect, the Odisha government on Tuesday announced a state holiday and a seven-day state mourning.
Odisha Chief Minister Naveen Patnaik, Governor S.C. Jamir, several ministers and many political leaders expressed their condolence.