Undescribed morphological features of Adelphydraena amazonica Perkins Ribera, 2020 are provided based on material collected in the type locality (Amazonas State, northern Brazil). Aedeagus, male sternite X, last female abdominal segments and spermatheca are illustrated and described for the first time. Habitat information on the type locality is also included. New records on two Brazilian Hydraenidae species are provided.