About 90 per cent of the 2.29 million who cast ballots voted to split from Spain, as Catalans who reject independence largely boycotted the illegal poll.
The October 1 referendum voting for secession was severely repressed by police.
On Sunday, hundreds of thousands of Spanish flag-waving demonstrators packed central Barcelona to protest against the independence plan.
Demands for independence in Catalonia, which has its own language and cultural traditions, date back centuries.
Spain's separatism crisis faced a decisive moment on Tuesday with Catalonia's leader Carles Puigdemont set to address regional lawmakers in a speech his supporters hope will be a unilateral declaration of independence.
Whether the 54-year-old Catalan president will actually go ahead with it in defiance of the central government and national courts, play for time or simply back down is still a mystery.
At stake is the future of a region of 7.5 million people, one of Spain's economic powerhouses whose independence drive has raised concern for stability in the European Union.
Political leaders in Catalonia, Spain and Europe have urged Catalan separatists to back down and ease the country's biggest upheaval since it returned to democracy in the 1970s.
But Puigdemont says an independence referendum that took place on October 1 despite a ban by Madrid justifies secession.
About 90 per cent of the 2.29 million who cast ballots voted to split from Spain, as Catalans who reject independence largely boycotted an illegal poll that was severely repressed by police.
Puigdemont hinted in a weekend interview that the region would go ahead with the declaration if Madrid continued to refuse dialogue.
"We have said yes to so many mediation options that have been proposed," he told Catalan broadcaster TV3.
"The days are going by and if the Spanish state does not give a positive response, we will do what we set out to do."
Such a move "will not go unanswered by the government", Deputy Prime Minister Soraya Saenz de Santamaria retorted on Monday.
"If this gentleman unilaterally declares independence, measures will have to be taken," she told the COPE radio station.
Prime Minister Mariano Rajoy at the weekend refused to rule out an unprecedented constitutional manoeuvre to impose direct rule on the semi-autonomous region — a move likely to heighten tensions still further.
Catalan separatists have come under intense pressure both at home and abroad to halt plans to break away from Spain.