Background: Medication reconciliation is critical for preventing medication discrepancies and adverse drug events (ADEs) during hospital transitions. This study aimed to evaluate the impact of pharmacist-nurse collaboration on medication reconciliation, focusing on its effect on medication discrepancies, ADEs, hospital length of stay, and 30-day readmission rates. Methods: A prospective, interventional study was conducted at a tertiary hospital, involving 300 patients. The intervention group (n = 150) received pharmacist-nurse collaboration during medication reconciliation, while the control group (n = 150) followed standard care without interdisciplinary collaboration. Outcomes included the number of medication discrepancies, incidence of ADEs, length of hospital stay, 30-day readmission rates, and patient satisfaction. Results: The intervention group had significantly fewer medication discrepancies at discharge (0.8 vs. 2.7, p < 0.001) and a lower incidence of ADEs (9% vs. 18%, p = 0.034). Additionally, the intervention group experienced shorter hospital stays (5.8 vs. 7.1 days, p = 0.011) and lower 30-day readmission rates (10% vs. 17%, p = 0.045). Patient satisfaction was higher in the intervention group (94% vs. 76%, p < 0.001). Conclusion: Pharmacist-nurse collaboration significantly reduces medication discrepancies and ADEs, improves patient outcomes, and enhances patient satisfaction. This interdisciplinary approach should be integrated into routine hospital practices to improve the quality of care during transitions.