He completed his elementary education at De La Salle College in Manila before returning to Negros due to the Second World War.

Locsin then returned to Manila to finish his secondary education in La Salle and studied Pre-Law before shifting to pursue a Bachelor's Degree in Music at the University of Santo Tomas.

John Delaney, S.J., then Catholic Chaplain at the University of the Philippines - Diliman, commissioned Locsin to design a chapel with an open plan and can easily accommodate 1,000 people.

The Church of the Holy Sacrifice is the first round chapel in the Philippines to have an altar in the middle, and the first to have a thin shell concrete dome.

In 1969, he completed what was to be his most recognizable work, the Theater of Performing Arts (now the Tanghalang Pambansa) of the Cultural Center of the Philippines.

A large lagoon in front of the theatre mirrors the building during daytime, while fountains are illuminated by underwater lights at nighttime.

In 1974, Locsin designed the Folk Arts Theater, which is one of the largest single-span buildings in the Philippines with a span of 60 metres (200 ft).

After the Federico Ilustre-designed original terminal of Manila International Airport was destroyed by a fire in 1962, the Philippine government chose Locsin for the rehabilitation design.

Most of his work is concentrated in the Freedom Park, with the Student Union Building which was once damaged by a fire, the Carillon, the Continuing Education Center and the auditorium.