Purpose <p>[¹⁷⁷Lu]Lu-PSMA-617 therapy has emerged as a promising radioligand treatment for metastatic castration-resistant prostate cancer (mCRPC). Given the overall poor prognosis of mCRPC, accurately predicting the key endpoint overall survival (OS) remains an ongoing challenge, crucial for optimizing risk/benefit assessment prior to treatment. This study investigates the prognostic utility of the simple designed Bellmunt Risk Score (BRS) in mCRPC patients treated with [¹⁷⁷Lu]Lu-PSMA-617.</p> Methods <p>We retrospectively evaluated data from 386 mCRPC patients who had received [¹⁷⁷Lu]Lu-PSMA-617 therapy at our center. BRS was constructed by attributing one point for each of the following risk factors: ECOG performance status (ECOG PS) &gt; 0, hemoglobin &lt; 10&#xa0;g/dL, and the presence of liver metastases. Additionally, an enhanced version of the score including C-reactive protein (CRP) &gt; 30&#xa0;mg/dL and a modified version utilizing a semi-quantitative ECOG PS were developed. Statistical analysis included Cox regression, Kaplan-Meier estimates, concordance indices and time-dependent area under the curve (tAUC).</p> Results <p>The BRS served as an independent predictor of OS in multivariable analysis. The estimated median OS was 17.6, 10.9, 6.6, and 2.7 months for patients with scores of 0, 1, 2 and 3, respectively (Log-Rank <i>P</i> &lt; 0.001). The tAUC values for predicting 1-year and 2-year OS were 71.6% and 74.4%, respectively. The CRP-enhanced score further improved prognostic accuracy, achieving tAUCs of 75.7% for 1-year OS and 78.1% for 2-year OS.</p> Conclusion <p>The Bellmunt Risk Score effectively stratifies mCRPC patients undergoing [¹⁷⁷Lu]Lu-PSMA-617 therapy. Its straightforward design, based on readily accessible clinical parameters, ensures practicality and utility in real-world clinical settings.</p>