The fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is a polyphagous species which attacks many economically important crops in several countries. This insect is an important pest of corn, and currently the most widely used control method is chemical. In order to minimize environmental impacts, other forms of control have been tried, and accordingly, the investigation of plants with insecticidal effects becomes relevant. Thus the present study was conducted in order to evaluate the effect of the ethanolic extract of Euphorbia pulcherrima (poinsettia) leaves in fall armyworm biology. Extracts were prepared from leaves of the plant E. pulcherrima collected at different phenological stages (vegetative and reproductive), oven dried, crushed and then solubilized in ethanol, yielding the ethanol extract. The extracts were set aside in 0.5 and 1% concentrations for each phenological stage of the plant, incorporated into an artificial diet and offered to the larvae of S. frugiperda. The extract of vegetative and reproductive phase of E. pulcherrima leaves in concentrations of 0.5 and 1%, has showed that it affected mortality in the larvae, increasing the larval period and reducing the weight of larvae and pupae and viability of the eggs of the caterpillars. Ethanolic extract of E. pulcherrima leaves in the reproductive phase of the plant is effective to reduce the S. frugiperda population.