The need for new bioinsecticidal compounds motivates the study of natural products. Therefore, we studied the activity of Crescentia alata Kuth (Lamiales: Bignoniaceae) against Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae). We showed that C. alata has bioinsectidal activity. After 7 days of exposure to C. alata fractions in the diet at 200 ppm, fractions 3, 4 and 7 caused 90.7% weight loss in the larvae, and at 100 ppm, fractions 2, 4, 7 and 8 caused 90.1% weight loss with respect to the control. After 14 days of exposure to fractions 4 and 7 at 200, 100, and 50 ppm, the larvae had lost 94% of their weight compared to the control. There were large differences in larval mortalities between treatments, and fractions 5 and 6 at 200, 100, and 50 ppm induced the highest mortalities, which ranged from 65 to 80%. Possibly the iridoids identified from the C. alata fruit fractions are responsible for the antifeedant activity and mortality of S. frugiperda. This is the first report of C. alata fractions being evaluated as biocides of S. frugiperda.