Born and raised in Watsonville, Alejo's family came to work in the agricultural fields of the Salinas, Santa Clara and Pajaro Valleys as migrant farmworkers in the 1950s.

Alejo graduated from the University of California, Berkeley with dual bachelor's degrees in political science and Chicano studies, and obtained his master's of education degree from Harvard University in administration, planning and social policy.

He received his Juris Doctor (JD) from the University of California, Davis School of Law (King Hall), where he won the "Maggie Schelen" scholarship for public service.

[4] Prior to his public service, Alejo served as a Jesse M. Unruh Assembly Fellow where he worked as a legislative aide for Assemblymember Manny Diaz (D-San Jose).

[6][7] Alejo was elected in June 2016 to represent District 1 on the Monterey County Board of Supervisors.