The present study had as objective to evaluate the activity of limonoid azadiractin, extracted of the seeds of the plant Azadirachta indica, neem, on the embryonary development of Ctenocephalides felis felis. A dog was sprayed with the formulation 10%, another dog was kept as control, without treatment. Both had been infested weekly with 600 fleas, in the ratio of 1:1 between males and females. The deriving positions of the infestations had been incubate per seven days in assay pipes, and evaluated it percentage of emerging of flea eggs, comparing themselves the averages of the groups treat and have controlled. The extract of nim presented activity on the embryonary development of C. f. felis, keeping superior levels of effectiveness 80% until day +14, beyond diminishing the position and inhibiting the development between urging larval of the percentage of larvae that had come out.