The Brazilian Megalopodidae fauna consists of 147 species from 11 genera, of which Mastostethus Lacordaire is the most diverse, representing about half of the species. Nevertheless, knowledge about species distributions and their relationships with host plants is still scarce. Since this group has endophytic immatures and bore into branches, they are economically important as they mainly damage Solanaceae species. Thus, this study sought to determine the Megalopodidae species that occur in forest fragments of southwestern and western Paraná and associate them with their host plants. For this purpose, we used material collected with Malaise traps and active manual sampling to determine associations with host plants. A total of 170 specimens of 11 species were sampled, of which Pseudhomalopterus carinatus Pic, 1920 was the most abundant and collected in all fragments. Four species were sampled exclusively through manual collections and associated with their host plants, all of which were new association records for Brazilian megalopodides. Mastostethus pantherinus Lacordaire, 1845 was associated with an Asteraceae for the first time. Additionally, Mastostethus minutus Monrós, 1947 is a new record for Brazil.