Commissioned as a 2nd lieutenant thru the Army ROTC program on June 7, 1976 in the Puerto Rico National Guard.

His first assignment was as an Assistant Finance Officer, Alpha Company, 192d Support Battalion, Puerto Rico Army National Guard in San Juan, Puerto Rico.

Certified Defense Financial Manager (CDFM) American Association of Military Comptrollers.

During his tenure as Adjutant General of the Puerto Rico National Guard, Rivera led the PRNG during the recovery relief efforts after the path of Hurricane Maria thru Puerto Rico.

Isabelo Rivera resigned the position as Puerto Rico Adjutant General to retire after 42 years of military service.