We recorded the occurrence of the African catfish Clarias gariepinus in the inland waters of southeastern Puerto Rico for the first time, increasing the number of exotic freshwater fish on the island. Two individuals of C. gariepinus were collected in the municipality of Guayama and deposited in a zoology collection. This opportunistic species represents a serious concern due to the reported adverse ecological impact on native ecosystems. The source of the introduction remains unclear, but we suggest the aquarium trade or fish farmers as two potential sources. Further studies are important to control the expansion of C. gariepinus in Puerto Rico.