Cotesia flavipes (Cameron) is a parasitoid responsible for maintaining populations of sugarcane borer, Diatraea saccharalis (F.), below economic levels in south Texas sugarcane fields. Transgenic sugarcane expressing the snowdrop lectin (Galanthus nivalis agglutinin, GNA) was developed against the Mexican rice borer, Eoreuma loftini (Dyar), the primary pest of south Texas sugarcane. The potential impact of GNA-expressing sugarcane on various biological and fitness parameters of Cotesia flavipes (Cameron) was studied in the laboratory to gain insight on likely effects of the transgenic sugarcane on biological control of sugarcane borer by C. flavipes. Females of C. flavipes were offered sugarcane borer larvae fed one of two diet treatments for oviposition for two successive generations: (1) artificial diet containing transgenic sugarcane tissue or (2) artificial diet containing nontransgenic sugarcane tissue. Small to marginal negative effects of artificial diet containing transgenic sugarcane tissue were evident in the rate of host suitability, number of cocoons and adult parasitoids emerging per host, percentage cocoons yielding parasitoids, and sex ratio and adult lifespan of parasitoids. These effects were variable between the two parasitoid generations examined. In contrast, differences were not detected between diet treatments in rates of host acceptance, egg load of females, and egg to adult developmental periods. The negative effects of transgenic sugarcane on C. flavipes detected in this study are important because GNA levels in the diet (≈0.49% of total protein content) containing transgenic sugarcane tissue were ≈50% of the level expressed in transgenic sugarcane plants. Results are discussed in relation to potential impacts of the transgenic cultivar on biological control of sugarcane borer by C. flavipes.