Steinernema puertoricensis n. sp., isolated from sand collected from a coconut plantation, can be distinguished from S. glaseri, its most closely related species, by characteristics of the first generation adults. The female has a greater body length (8.6 mm) and width (375 µm). Males have the excretory pore anteriad or posteriad to the nerve ring. Spicules are arcuate and lack a hook at the ventral side of the spicule tip. Infective third-stage juveniles are over 1 mm in length. This appears to be the first species of Steinernema described from the Caribbean islands and adapted to a hot humid environment.