The ferns flora of Sulawesi is poorly documented. Pteris L. is a large fern genus inhabiting various habitats, mostly forests, which are distributed in tropical and subtropical countries. Floristic study on fern genus Pteris in the karst forests of Bantimurung Bulusaraung National Park (BabulNP) was carried out to add our knowledge of the ferns flora of Sulawesi. This study aimed to inventory Pteris growing in the karst forest of BabelNP and determine the rarity of each species. Nine species were recorded, namely, Pteris biaurita L., P. ensiformis Burm.f., P. longipes D. Don, P. pellucida C. Presl, P. radicans Christ., P. quadriaurita Retz., P. spinescens C. Presl., P. tripartita Swartz, and P. vittata L.. P. pellucida and P. spinescens may be new records for Sulawesi. Summary of the most important characters for distinguishing species of Pteris in the park is provided. Five species, namely Pteris longipes, P. pellucida, P. quadriaurita, P. radicans, and P. spinescens are considered as rare species. This study contributes to the knowledge of Malesian biodiversity, especially for fern flora of Sulawesi growing on karst forest. This survey provides baseline data for one of the most dominant elements of the understory cover in the limestone forests of BabulNP.