Serrano was born 26 April 1945 in Guatemala City as the son of Jorge Adán Serrano and Rosa Elías, who was of Lebanese descent. After attending school in Switzerland he graduated in industrial engineering from the University of San Carlos, and then attended Stanford University in California, U.S., where he studied economic growth and gained a doctorate in education and science. He then returned to Guatemala to become a civil servant. In 1976 he collaborated with various American Protestant churches to help the population recover from the devastating earthquake that had afflicted the country. He then published a document describing the miserable conditions under which the indigenous population lived, which resulted in his receiving threats. He went into exile in the US, only returning in 1982, to work in the government of fellow evangelical General Efraín Ríos Montt as Vice President of the Advisory Board to the government.