For this report, we studied the conventional karyotype and the NOR-bearing chromosomes in the toadfish Halobatrachus didactylus. We found a karyotype of 46 chromosomes made up of 8 metacentric, 12 submetacentric, and 26 acrocentric elements (FN = 66). No heteromorphic sex chromosomes were observed in the species. Metacentric chromosomes were easily classified as homologous pairs according to their morphology and L/S ratio. The rest of the chromosomes could not be accurately classified as homologous pairs because differences in chromosome size and L/S ratio were too slight between adjacent pairs within a size-ranged series. A single pair of NOR-bearing chromosomes was found. Active NORs were terminally located in a submetacentric pair of chromosomes.Se estudió el cariotipo del pez sapo marino. El número de cromosomas. La ausencia de cromosomal sexuales heteromórficos. Lso cromosomas metacéntricos fueron facilmente clasificados y el resto de cromosomas no pudo ser clasificado con precisión.Peer reviewed