Background <p>Positive surgical margins (PSM) after laparoscopic radical prostatectomy are a critical factor influencing treatment outcomes and prognosis in prostate cancer. Optional treatment strategies (neoadjuvant therapy, surgical techniques) and intraoperative margin monitoring highlight the importance of PSM risk assessment. This study aims to evaluate the potential PSM risk in transitional zone (TZ) tumors.</p> Materials and methods <p>This retrospective study included 434 patients who underwent laparoscopic radical prostatectomy after multiparametric magnetic resonance imaging at our center between 2019 and 2023.</p> Results <p>The PSM rate was significantly higher in patients with TZ lesions compared to those with peripheral zone lesions (47%, <i>n</i> = 175 vs. 28%, <i>n</i> = 226, <i>p</i> &lt; 0.01). Lesion location in TZ (OR: 4.29, 97.5% CI: 2.60–7.23, <i>p</i> &lt; 0.01) was identified as independent risk factors for PSM. Further analysis identified largest dimension of lesions (OR: 1.27, 97.5% CI: 1.09–1.50, <i>p</i> &lt; 0.01) and the number of positive biopsy cores (OR: 1.39, 97.5% CI: 1.16–1.70, <i>p</i> &lt; 0.01) as independent risk factors for PSM in patients with TZ tumors. LASSO regression identified four significant variables (largest dimension of lesions—the most important variable, number of positive biopsy cores, prostate-specific antigen density, and International Society of Urological Pathology grade). These variables were used to construct three PSM risk prediction models, each demonstrating favorable predictive accuracy and clinical benefit.</p> Conclusions <p>Certain TZ prostate cancer patients demonstrate a higher predisposition to PSM occurrence. Lesion dimension as a significant predictor of PSM for TZ patients. Separate PSM risk assessments for subgroups, like TZ prostate cancer patients, may enhance predictive accuracy and clinical utility.</p> Clinical trial registration <p>China Clinical Trial Registry (ChiCTR2300075944, 2023).</p>