Lucilia sericata larval secretions have bacteriostatic and bactericidal effects. We investigated the effect of L. sericata larval secretions during passage from the third to the second stage on Leishmania tropica under in vitro and in vivo conditions. The L. sericata larvae and their secretions were also used in the treatment of cutaneous leishmaniasis lesions. A total of 29 patients were included in this study. Seven patients were infected with Glucantime-resistant Leishmania major. In 22 patients, there was no information about the Glucantime resistance status and infection with L. tropica or L. major. All patients were efficiently treated with L. sericata larvae and their secretions without leaving scar tissue. Additionally, after 1-2 months of treatment, Leishmania spp. was not detected in the samples using PCR.