Purpose <p>To assess the effectiveness of prophylactic laxative use compared to symptom-based management for preventing constipation in patients undergoing surgery for urological cancers.</p> Methods <p>Of 2,024 screened patients (aged 18–80) with urological tumors, 1,724 eligible (no severe gastrointestinal disease, non-pregnant, scheduled for surgery) were non-randomly assigned to prevention (prophylactic laxatives, <i>n</i> = 965) or non-prevention groups (symptom-based, <i>n</i> = 748). Propensity score matching with a 1:1 optimal matching strategy was used to minimize baseline differences between the two groups. The primary outcome was the incidence of constipation within 7 days post-surgery. Secondary outcomes included complete spontaneous bowel movements (CSBM), patient assessment of constipation quality of life (PAC-QOL) scores, and patient assessment of constipation symptoms (PAC-SYM) scores at 7 days post-surgery. A nomogram was developed for predicting postoperative constipation.</p> Results <p>Compared to non-prevention, the incidence of postoperative constipation was significantly lower in the prevention group (12.3% vs. 42.7%; HR 0.24, 95% CI: 0.19–0.30, <i>P &lt;</i> 0.001). A higher proportion of patients in the prevention group achieved ≥ 3 CSBMs per week ( 96.0% vs. 88.2%, <i>P &lt;</i> 0.001), and PAC-SYM mean difference (MD = − 0.56, 95% CI: −0.79 to − 0.33) and PAC-QOL (MD = − 1.22, 95% CI: −2.03 to − 0.41) scores were improved. Age, constipation diagnosis, prophylactic laxative use, and baseline CSBM were identified as independent risk factors for postoperative constipation.</p> Conclusion <p>Prophylactic laxative use was associated with a significantly lower incidence of postoperative constipation in patients with urological tumors. Our findings offer preliminary evidence for clinicians in identifying patients at risk of developing postoperative constipation.</p> Trial registration <p>ChiCTR2100042876 (<a href="http://www.chictr.org.cn">www.chictr.org.cn</a>).</p>