We investigate the effect of chitosan coatings to kill the immature stages of Anastrepha ludens (Mexican fruit fly) in mango fruits (cv. Ataulfo). The fruits were effectively infested after exposure of 4 h to gravid females. Larvae of first, second and third instars were found inside the fruits 3, 7 and 10 d after oviposition. No embryos, first or second larval instar was developed when the fruits were coated 0.5, 2, 4 and 8 d after oviposition. We suggest the mass transfer (CO2 and O2) modification can be implicated in those results. In contrast, application of chitosan after 10 d of oviposition did not kill the insects. In this case, more of 90% of the insects emerge as adult flies, value similar to the developed in uncoated fruits. The main reason for this result was that the fruits had significant loss of firmness and it difficult the homogeneous formation of chitosan coating.