Pessaries are an effective treatment for pelvic organ prolapse, yet currently available pessaries can cause discomfort with removal and insertion. An early feasibility trial of an investigational, collapsible pessary previously demonstrated mechanical feasibility during a brief 15-minute office trial. Longer-term, patient-centered safety and efficacy data is needed. To assess the effectiveness and safety of the investigational vaginal pessary for pelvic organ prolapse at three months. This was a prospective, seven-center, open-label equivalence study with participants serving as their own controls. Subjects were current users of a Gellhorn or ring pessary with ≥ Stage II prolapse. Baseline subjective and objective data were collected for one month using their current pessary, and then data were collected through a three-month treatment phase with use of the study pessary. The primary outcome was change in Pelvic Floor Distress Inventory-20 score. Secondary outcome measures included objective assessment of prolapse support, changes in the Pelvic Floor Impact Questionnaire-7, and pain with insertion and removal measured on a Visual Analog Scale. Subjects fitted with study pessary were analyzed as intention to treat and those who dropped out were assigned scores at the upper limit of the predefined equivalence limits. Secondary per protocol analyses included subjects who completed treatment. The study was powered to 80% with a minimal important change equivalence limit of 18.3 points on the Pelvic Floor Distress Inventory-20 scale. Square root transformations were used for non-parametric data and p-values adjusted for multiple comparisons. Seventy-eight subjects were enrolled, though 16 withdrew prior to study pessary placement. Sixty-two subjects (50 ring and 12 Gellhorn pessary users) were fitted with the study pessary, and 48 (62%) completed the three-month intervention. The change in Pelvic Floor Distress Inventory-20 scores at three months demonstrated equivalence compared to the subjects' baseline scores, (mean difference -3.96 (improvement), 90% confidence interval (CI) [-11.99, 4.08], p=0.002). Per protocol analysis of the Pelvic Floor Distress Inventory-20, equivalence was not demonstrated with scores favoring the study pessary (mean difference -10.45, 90% CI, [-20.35, 0.54] (p=0.095)). Secondary outcomes included: objective measures of support which were similar, mean difference Ba=0.54 cm, Bp=0.04 cm, favoring study pessary; improvement in mean Pelvic Floor Impact Questionnaire-7 scores for those who completed the trial (pre=32.23, post=16.86, p=0.019); and pain with insertion and removal, which was lower with the study pessary compared to subject's own pessary (mean difference Visual Analogue Scale insertion=9.91 mm (p=0.019), removal=11.23 mm (p=0.019)). No serious adverse events related to the pessary were reported. Equivalence was demonstrated in the study pessary primary outcome compared to current non-collapsible pessaries for change in severity and bother of pelvic floor symptoms. In participants who completed the trial, the Pelvic Floor Impact Questionnaire-7 improved with the study pessary and change in Pelvic Floor Distress Inventory-20 scores were non-equivalent, favoring the study pessary. Subjects reported significantly lower pain scores with both pessary insertion and removal with the novel collapsible pessary compared with their standard pessary.