According to reports, Patekar, who was living with his nephew Prasad Patekar, had complained of a headache since Wednesday night.
He was found unconscious at his residence in Dona Paula in the early hours of Thursday and was subsequently rushed to Manipal Hospital.
Doctors attempted to revive the actor for around 45 minutes, but he did not respond to the treatment. He was declared dead at around 5:20 am, according to hospital sources.
Patekar's son Malhar Patekar, who was in Pune, has reportedly left for Goa following the news of his father's death.
Nana Patekar's illustrious career
Born Vishwanath Patekar, Nana Patekar began his acting journey in theatre before making his film debut with the 1978 Hindi film Gaman.
Over the following four decades, he established himself as one of Indian cinema's most distinctive actors, known for his intense performances, powerful dialogue delivery and ability to portray both serious and comic characters.
He shot to wider prominence with films such as Parinda (1989), for which he won the National Film Award for Best Supporting Actor, and went on to deliver acclaimed performances in Angaar, Tirangaa, Krantiveer, Agni Sakshi and Khamoshi: The Musical.
Patekar won the National Film Award for Best Actor for Krantiveer and another National Film Award for Best Supporting Actor for Agni Sakshi. He also earned praise for his performances in films including Ab Tak Chhappan, Apaharan, Raajneeti and the Welcome franchise.
He also ventured into filmmaking, making his directorial debut with Prahaar: The Final Attack.
Patekar continued to work in both Hindi and Marathi cinema, earning critical acclaim for his performance in the Marathi film Natsamrat (2016).
A recipient of the Padma Shri, Patekar leaves behind a career spanning more than four decades and a body of work that included acting, writing and direction.