El Salvador is the smallest and most densely populated country in Central America. It is well into its demographic transition, experiencing slower population growth, a decline in its number of youths, and the gradual aging of its population. The increased use of family planning has substantially lowered El Salvador's fertility rate, from approximately 6 children per woman in the 1970s to replacement level today. A 2008 national family planning survey showed that female sterilization remained the most common contraception method in El Salvador - its sterilization rate is among the highest in Latin America and the Caribbean - but that the use of injectable contraceptives is growing. Fertility differences between rich and poor and urban and rural women are narrowing.

Salvadorans fled during the 1979 to 1992 civil war mainly to the United States but also to Canada and to neighboring Mexico, Guatemala, Honduras, Nicaragua, and Costa Rica. Emigration to the United States increased again in the 1990s and 2000s as a result of deteriorating economic conditions, natural disasters (Hurricane Mitch in 1998 and earthquakes in 2001), and family reunification. At least 20% of El Salvador's population lives abroad. The remittances they send home account for close to 20% of GDP, are the second largest source of external income after exports, and have helped reduce poverty.