Background <p>Lymphatic leakage is a common complication after radical cystectomy and pelvic lymph node dissection (PLND) for muscle-invasive bladder cancer (MIBC).This study aimed to investigate the risk factors contributing to postoperative lymphatic leakage in patients with MIBC.</p> Materials and methods <p>A total of 534 patients undergoing radical cystectomy and PLND were enrolled in the retrospective study at Peking University Third Hospital from January 2010 to July 2023. Patients were categorized into lymphatic leakage(<i>n</i> = 254)and non-leakage groups (<i>n</i> = 280) and compared demographic, perioperativ and pathologic factors. Multivariate logistic regression was applied to identify risk factors for lymphatic leakage. Spearman correlation was used to analyze the relationship between lymph leakage ratio and risk factors.</p> Results <p>Patients with lymphatic leakage had significantly higher rates of receiving extended PLND (19.7% vs. 11.4%, <i>p</i> = 0.008), higher total number of dissected lymph nodes (median 11 vs. 8, <i>p</i> &lt; 0.001), longer hospital stays (median 13 vs. 11 days, <i>p</i> &lt; 0.001), higher postoperative hypoalbuminemia rate (56.7% vs. 36.4%, <i>p</i> &lt; 0.001) and higher fever rate (14.2% vs. 8.6%, <i>p</i> = 0.04) compared to the non-leakage group. On multivariate analysis, higher number of dissected lymph nodes (OR 3.278, 95% CI 1.135–9.471, <i>p</i> = 0.028) was found to be a independent risk factor for lymphatic leakage. Additionally, a positive correlation was observed between the numbers of dissected lymph nodes and lymphatic leakage rate (<i>R</i> = 0.456, <i>p</i> = 0.013).</p> Conclusions <p>The increased number of dissected lymph nodes is associated with a heightened risk of lymphatic leakage following radical cystectomy for MIBC.</p>