The mammalian cochlear nucleus contains specialized neurons called Octopus Cells that are responsible for detecting simultaneous complex frequencies. These cells are recognizable by their unique morphology of their thick and unidirectional branching dendrites that stretch across tonotopically arranged auditory nerve fibers from the cochlea. During postnatal development of mice, these cells undergo significant changes in morphology around 12 days after birth (P12), which corresponds to the onset of hearing. Data were obtained from Mice before, during, and post-hearing onset (P8, P12, and P16) using trans-cardial perfusion, chromogenic immunohistochemistry techniques, and 3D reconstructions of the cells. The total dendritic length and number of Sholl intersections increase significantly at P12 and decrease at P16, suggesting that after hearing onset (P12), the octopus cells go through an additional morphological refinement of their dendrites at around P16.