Introduction and Hypothesis <p>This study aimed to investigate the relationship between preoperative pelvic floor muscle (PFM) strength and the efficacy of tension-free vaginal tape-obturator (TVT-O) surgery in women with stress urinary incontinence (SUI).</p> Methods <p>Two hundred women diagnosed with SUI who underwent TVT-O surgery were included. PFM strength was assessed preoperatively using a validated digital palpation method. The evaluation of the effectiveness of surgical treatments for SUI was based on standardized criteria for urine leakage during stress conditions, changes in the 1-h pad test urine volume compared to preoperative levels, and the postoperative IIQ-7 scores. Patients were classified into “improved” and “unimproved” groups. Univariate and multivariate logistic regression models were used to analyze the association between PFM strength and postoperative improvement.</p> Results <p>A total of 170 patients were categorized as the improved group, while 30 patients were classified in the unimproved group. The improved group demonstrated a mean PFM strength of 3.5 ± 1.4 cmH2O vs. 2.8 ± 1.2 cmH2O (<i>p</i> &lt; 0.01). In both univariate and multivariate logistic regression analyses, PFM strength was significantly associated with postoperative improvement, with odds ratios of 2.8 (95% CI 1.4 to 5.5, <i>p</i> = 0.004) and 2.5 (95% CI 1.2 to 5.0, <i>p</i> = 0.01), respectively. Subgroup analyses revealed that the association was particularly strong in postmenopausal women, multiparous patients, and those with comorbidities.</p> Conclusion <p>Preoperative PFM strength is significantly associated with the efficacy of TVT-O surgery for SUI. This study highlights the importance of PFM strength in predicting surgical outcomes and suggests that preoperative assessment of PFM strength may help in optimizing patient selection for SUI patients undergoing TVT-O.</p>