Stress urinary incontinence (SUI) is the involuntary release of urine during sudden increases of abdominal pressures. SUI is common in women after vaginal delivery or pelvic trauma, and may alter the biomechanical properties of the urethra. Thus, we hypothesize that injury due to vaginal distension (VD) decreases urethral basal tone and passive stiffness. This study aimed to assess the biomechanical properties of the urethra after VD in the baseline state, where basal muscle tone and extracellular matrix (ECM) are present, and in the passive state, where inactive muscle and ECM is present. Female rat urethras were isolated in a rat model of acute SUI induced by simulated birth trauma. Our ex vivo system was utilized, wherein we applied intralumenal static pressures ranging from 0 to 20 mmHg. Outer diameter was measured via a laser micrometer. Measurements were recorded via computer. Urethral thickness was assessed histologically. Stress-strain responses of the urethra were altered by VD. Quantification of biomechanical parameters indicated that VD decreased baseline stiffness. The passive peak incremental elastic modulus of the distal segment in VD urethras was less than for controls (1.84±0.67|*10⁶ dynes/cm² vs. 1.19±0.70*10⁶dynes/cm², respectively; p=0.016). An increase was noted in passive low pressure compliance values in proximal VD urethras compared to controls (9.44±2.43 mmHg^-1 vs. 4.62±0.60mmHg^-1, respectively; p=0.04). Biomechanical analyses suggest that VD alters urethral basal tone, proximal urethral compliance, and distal stiffness. Lack of basal smooth muscle tone, in combination with these changes in the proximal and distal urethra, may contribute to SUI induced by VD.