Introduction and hypothesis: The aim of the study was to determine whether successful incontinence pessary fitting or pessary size can be predicted by specific POPQ measurements in women without advanced pelvic organ prolapse. Methods: In a multicenter study, women with stress urinary incontinence (SUI) and POPQ stage ≤2 were randomized to three treatment arms: (1) incontinence pessary, (2) behavioral therapy, or (3) both. This study evaluates incontinence pessary size, POPQ measures, and successful fitting in the 266 women assigned to treatment arms 1 and 3. Results: Two hundred thirty-five women (92%) were successfully fitted with an incontinence ring (n = 122) or dish (n = 113). Hysterectomy, genital hiatus (GH), and GH/total vaginal length (TVL) ratios did not predict unsuccessful fitting (p > 0.05). However, mean TVL was greater in women successfully fitted (9.6 vs. 8.8 cm, p < 0.01). Final pessary diameter was not predicted by TVL, point D, or point C (p > 0.05). Conclusions: The vast majority of women with SUI can be successfully fitted with an incontinence pessary, but specific POPQ measures were not helpful in determining incontinence pessary size.