Sediment samples were taken during a short-term study of the distribution of meiofauna from a coastal lagoon in Sinaloa (northwestern Mexico). Several species of harpacticoids (Copepoda: Harpacticoida) were observed among the taxa recovered. Some of these species are new to science, whereas some others are new records for Mexican brackish systems. Three species of Apodopsyllus (Harpacticoida: Paramesochridae) are described herein. One of them, A. alejandrovillalobosi sp. nov. proved to be closely related to its northern congener A. vermiculiformis known from California and British Columbia. Apodopsyllus samuelgomezi sp. nov. and A. pseudocubensis sp. nov. constitute new records of the neotropical arcuatus-chilensis-cubensis lineage. Apodopsyllus samuelgomezi sp. nov. is unique within this clade in the male P6 with two long inner setae. Apodopsyllus pseudocubensis sp. nov. was found to be allied to its Cuban relative A. cubensis. These two species share the general shape of female P5 and male P6.