"We welcome the decision made today by the Eurogroup to grant financial assistance from the European Financial Stability Fund to Spain to recapitalize its banking sector," Lagarde said in a statement.
"The recapitalization of weak banks and the other reforms attached to the agreement are consistent with the IMF's recommendations," the IMF managing director said.
"The implementation of these measures will contribute to significantly strengthen Spain's financial system, an essential step in restoring growth and prosperity in the country."
Eurozone finance ministers on Friday announced an aid package for Spanish banks of up to €100bn ($122bn), saying it would help "safeguard financial stability in the euro area as a whole."