He lost his bid for re-election in February 2008.
His successor, Dimitris Christofias, expressed his condolences and said Papadopoulos was one of the key actors in Cyprus' modern history.
"From a young age, Tassos Papadopoulos dedicated his life to the freedom struggle of the Cypriot people and played a lead role for the Cyprus Republic's cause," Christofias said.
Christofias declared three days of mourning starting on Saturday. Papadopoulos' funeral will be held on Monday, and the day has been declared a public holiday.
Papadopoulos was a veteran of Cyprus politics. He was a leader of the Greek Cypriot guerrilla group EOKA, which waged the campaign against British colonial rule before Cyprus gained independence in 1960.
At 26, he became a minister in Cyprus' first post-independence government.
It was Papadopoulos who submitted a proposal in 1977 for a federated Cyprus tying together two distinct zones.
After several stints in parliament, he was elected leader of the centre-right Democratic party in 2000.
Karolos Papoulias, Greece's president, said Papadopoulos had "fought with passion and consistency for the future of Cypriot Hellenism ... always within the framework of democratic legality".
The Mediterranean island was divided in a Turkish invasion in 1974 triggered by a Greek-inspired coup to unite the island with Greece.