Lectins have demonstrated significant levels of protection against different pests when expressed in transgenic plants. The effects of the coagulant Moringa oleifera lectin (cMoL) on moth flour (Anagasta kuehniella) were tested by incorporating the protein in an artificial diet at levels of 0.5%, 1% and 2% (w/w), respectively. cMoL showed a dose-dependent effect on average larval weight and a series of nutritional disturbances. A significant increase in total development time of 15 days was observed in the group fed with cMoL at 1%, increasing the rate of pupal mortality by 27.6%. The A. kuehniellamidgut proteases were unable to digest cMoL for up to 12 h of incubation. The lectin presented a tight binding to a chitin column, suggesting that the insecticidal activity of cMoL involves carbohydrate–lectin interactions on the surface of the digestive tract, with glycoproteins and others glycolsylated structures in the midgut and resistance to enzymatic digestion.