Zambrano, who won three division championships over six seasons with Los Angeles (1997-1999) and the MetroStars (2000-02) was 80-55-8 as a head coach.
"We worked to add an assistant coach with head coaching experience," Wizards President Robb Heineman said. "Octavio has excellent knowledge of our league and the international game. His presence will allow Peter Vermes to focus both on day-to-day coaching of the team and player personnel decisions more easily."
Zambrano, 51, was born in Guayaquil, Ecuador and came to the United States in 1980 to attend Chapman University.
He has coached CS Tiligul-Tiras Tiraspol in Moldova (2006-08) and FC Tatabanya in Hungary (2008-09).
Kerry Zavagnin, Zoran Savic and John Pascarella will remain on the technical staff as assistant coaches.