The butterfly sanctuary at the La Union Botanical Garden (LUBG) is the largest of its kind in the Philippines in terms of butterfly population. This study gives the details of the species richness and diversity of butterflies and their food plants at LUBG. A total of 158 butterfly and 77 food plant species were collected and identified by standard methods. Butterfly and food plant species richness are well correlated with diversity and areal density in all vegetation types surveyed. The collections comprised 17 endemic and 18 rare butterfly species that are predominantly represented by the families Nymphalidae, Pieridae, Papilionidae, Danaidae, Satyridae and Lycenidae. The food plants were widely represented by the families Rubiaceae, Asteraceae, Apocynaceae and Verbenaceae, yielding high diversity indices in 3 out of 6 vegetation types. This study was able to assess the species richness and diversity of butterflies and their food plants at LUBG.