Jose Manuel Barroso said Spain had shown unwavering support for Europe
Spain's Senate has voted overwhelmingly to adopt the European Union's Lisbon Treaty, one month after it was rejected by Irish voters in a referendum.
King Juan Carlos must still sign the treaty, at which point Spain will become the 23rd EU state to ratify it.
The Lisbon Treaty must be ratified by all 27 EU member states to come into force. Only Ireland held a referendum.
European Commission President Jose Manuel Barroso said Spain had shown "unwavering support" for Europe.
"I believe that today's approval of the treaty is a clear confirmation of the determination to move forward with the ratification process," he said in a statement.
The treaty is intended to streamline EU decision-making following enlargement of the bloc, creating a new EU president and foreign affairs chief.
Meanwhile, French President Nicolas Sarkozy - who currently holds the rotating EU presidency - has reportedly said that Ireland must hold a second vote on the treaty, according to a French official.
Mr Sarkozy will visit Dublin next week.
EU leaders are due to meet in October to hear proposals from Ireland's prime minister about how to move forward after the "No" vote.