In most mammals, the accessory olfactory bulb (AOB) plays a key role in pheromone detection. The AOB network consists of excitatory projection neurons (mitral cells) and different groups of local interneurons that shape mitral cell activity. Granule cells (GCs) make up the most prominent interneuron type. They are connected to AOB mitral cells by reciprocal dendrodendritic synapses. While GCs play an essential role in AOB information processing, their physiological characteristics remain elusive. Here, we describe GC electrophysiological properties. Using whole-cell patch-clamp recordings in acute brain slices from wild type mice, we investigate cell type-specific features such as membrane properties, ion channel composition, spontaneous activity, and synaptic input. First, passive and active membrane properties differ from GCs in the main olfactory bulb. Moreover, within the AOB GC population, properties are heterogeneous, suggesting the existence of distinct GC subpopulations. Second, recordings reveal expression of voltage-gated potassium, sodium, and calcium channels as well as HCN channels. Third, a subset of cells displays spontaneous action potential firing at moderate frequencies. Finally, AOB GCs receive distinct patterns of synaptic input. Together, this research provides first insight into the physiological characteristics of AOB GCs, indicating diverse roles in AOB information processing.