The former New York Red Bulls, Columbus Crew and Earthquakes defender has spent the past three years with the Californian outfit as head of the club's youth academy, having finished his playing career with three years in San Jose from 2009-2011.
"I have been lucky enough to be a part of this organization for the past seven years and am excited for this opportunity," Leitch said in a statement released by the club.
"I would like to thank Dave Kaval and John Doyle and I am looking forward to working closely with them and our great coaching staff. In addition to building a strong first team, we are also committed to continuing to strengthen the connection between our first team and the academy."
The Earthquakes are currently in the midst of a six game winless run which has them sitting second bottom on the Western Conference table.