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 meters. It was completed in only seventy-seven days, in time for the Miss Universe Pageant. Locsin was also commissioned to build the Philippine International Convention Center, the country's premiere international conference building and now the seat of the Vice Presidency.
He was also commissioned in 1974 to design the Ayala Museum to house the Ayala art collection. It was known for the juxtaposition of huge blocks to facilitate the interior of the exhibition. Locsin was a close friend of the Ayalas. Before taking the board examination, he took his apprenticeship at Ayala and Company (Now the Ayala Corporation) and was even asked to design the first building in Ayala Avenue, and several of their residences. When the collection of the Ayala Museum was moved to its current location, the original was demolished with Locsin's permission. The current building was dedicated in 2004, and was designed by his firm, L.V. Locsin and Partners, led by his son Leandro Y. Locsin, Jr.