Introduction: Identifying the predictive factors of sustained return of spontaneous circulation (ROSC) following out-ofhospital cardiac arrest (OHCA) will be helpful in management of these patients. This study aimed to develop a predictive model in this regard. Methods: In a retrospective observational study, data of adult patients with OHCA, were collected from Vajira emergency medical services patient care report. Multiple logistic regression analysis with a regression coefficient was used to develop a predictive score for a sustained ROSC at the scene. Area under the receiver operating characteristic (ROC) curve (AUC) was used to validate the accuracy of the predictive score for a sustained ROSC. Results: Independent factors associated with a sustained ROSC included cardiopulmonary resuscitation (CPR) duration < 30 min (adjusted odds ratio (AOR)= 5. 05, 95% confidence interval (CI): 3. 34–, 7. 65,p < 0. 001),advanced airway management with an endotracheal tube (AOR= 3. 06, 95%CI: 1. 77–, 5. 31,p < 0. 001),advanced airway management with laryngeal mask airway (AOR= 3. 42, 95% CI: 1. 02–, 11. 46,p = 0. 046),defibrillation (AOR = 2. 05, 95% CI: 1. 31–, 3. 2,p = 0. 002),Capillary blood glucose (CBG) level < 150 mg% (AOR= 1. 95, 95% CI: 1. 05–, 3. 65,p = 0. 035),CBG at least 150 mg% (AOR= 2. 87, 95% CI: 1. 56–, 5. 29,p = 0. 001),pupil reflex (AOR = 2. 96, 95% CI: 1. 1–, 7. 96,p = 0. 032),and response time at most 8 min (AOR= 1. 66, 95%CI: 1. 07–, 2. 57,p = 0. 023). These were developed into the pupil reflex, response time, advanced airway management, defibrillation, CBG, and CPR duration (PRAD-CCPR) score. Themost accurate cutoff point of score using Youden’, s index was ¸,6 with AUC of 0. 759 (95% CI: 0. 715–, 0. 802,p < 0. 001), sensitivity of 62. 0% (95% CI: 51. 2–, 71. 9%), specificity of 75. 7% (95% CI: 69. 4–, 81. 2%), positive predictive value of 51. 8% (95% CI: 40. 9–, 62. 3%), and negative predictive value of 79. 5% (95% CI: 73. 5–, 84. 6%). Conclusion: An optimal PRAD-CCPR score of ¸,6 provides an acceptable accuracy of 0. 759 with sensitivity of 62. 0% and specificity of 75. 7% in prediction of sustained ROSC following OHCA. This predictive score might help CPR commanders to prognosticate the outcome of patients with OHCA at the scene.