Victor Sánchez Cerén won 50.11 percent of the vote. Competing ARENA party candidate Quijano has not yet acknowledged the FMLN's win.
Polls show the FMLN is a shoo-in for the presidency. But, they don't have a majority in the national assembly, limiting their power.
El Salvador's left-wing candidate won 49 percent of the vote, just short of the majority needed to secure victory in this weekend's election. The next round isn't expected to be an easy win.
El Salvador's presidential election takes place next month, and topics of gang violence, the economy, and healthcare are top of mind.
El Salvador's National Assembly reelected previously barred magistrates, moving a step toward national consensus that the Supreme Court has the last word on the country's Constitution.
Sunday's National Congress and mayoral elections in El Salvador are seen as a litmus test for President Mauricio Funes of the left-leaning Farabundo Marti Liberation Front (FMLN).
Critics say El Salvador's new Decree 743, which requires the Constitutional Court to make decisions by unanimous consensus, renders the court powerless.
A talk show host wins the presidential election. Will he be more like Venezuela's Chávez or Brazil's Lula?