In an astonishing plea for calm he claimed the groundwork had not yet been laid for a breakaway from Spain.
His calls for caution come as the Spanish government approved a law making it easier for companies to move their headquarters out of Catalonia immediately.
Arthur Mas was leader of the governing pro-independence party PDeCat and made Catalan independence a central party of his political agenda.
Speaking to the Financial Times he said: “We have won the right to be an independent country.
“The question now is how do we exercise that right, and here obviously there are decisions to be taken.
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“This is not just about proclaiming independence but about actually becoming an independent country.”
He said becoming completely independent would mean territorial control, tax collection and power over the judicial system would need to be handed over from Madrid.
He added if they can’t have control of those, it wouldn’t be “real” independence.
Mr Mas also emphasised the need to be pragmatic towards the likely backlash from the Spanish government.
The Catalonia parliament is to meet on Monday to discuss the referendum and what to do next, in defiance of Spain’s Constitutional Court who suspended the session.
Carles Puigdemont, the president of the Catalan regional government has requested to speak to lawmakers on Tuesday.
Putting pressure on the region, Madrid approved a decree to allow companies to move their headquarters out of Catalonia without requiring shareholders’ approval.
Banco de Sabadell and CaixaBank have already decided to move their legal headquarters out of Catalonia.
Energy company Gas Natural also announced it was temporarily moving its legal headquarters to Madrid.
Two million Catalans voted to split from Spain in Sunday’s referendum.
The referendum sparked violent clashes on October 1, and at least 893 civilians and 431 police officers were injured.
There have also been public spats between the two police forces, the Guardia Civil controlled by Madrid and the regional Mossos d’Esquadra force.
Spanish King Felipe Vl comdemned Sunday’s referendum in a national television address on Tuesday night and called Catalan leaders “disloyal”.