The number of men with type II diabetes-associated erectile dysfunction (ED) continues to grow rapidly, however, the majority of basic science studies have examined mechanisms of ED in animal models of type I diabetes. In this study, we first establish an in vivo mouse model of type II diabetic-ED using the leptin receptor mutated Db/db and wild-type control, BKS, mouse. Further, we hypothesized that dual mechanistic impairments contribute to the impaired erectile function in the type II diabetic mouse, altered vasoreactivity and veno-occlusive disorder. In vivo erectile function was measured as intracavernosal pressure (ICP) normalized to mean arterial pressure (MAP) following electrical stimulation of the cavernosal nerve. Veno-occlusion was assessed by the maintenance of elevated in vivo ICP following intracorporal saline infusion. Vasoreactivity of isolated cavernosum in response to contractile and dilatory stimulation was examined in vitro by myography. Collagen and elastin content were evaluated by quantification of hydroxyproline and desmosine, respectively, as well as by quantitative PCR and histological analysis of isolated cavernosum. Erectile function was significantly decreased in Db/db vs. BKS mice in a manner consistent with impairments in veno-occlusive ability and decreased inflow. Heightened vasoconstriction and attenuated dilation in cavernosum of Db/db vs. BKS mice suggest an overall lowered relaxation ability, and thus impaired filling of the cavernosal spaces. A decrease in desmosine and hydroxyproline, as well as lowered mRNA levels for tropoelastin, fibrillin-1, and 1(I) collagen were detected. These vasoreactive and sinusoidal matrix alterations may alter tissue compliance distensability, preventing the normal expansion necessary for erection.