BACKGROUND AND OBJECTIVES: Cardiovascular diseases (CVDs), including acute coronary syndrome (ACS), represent a major global health challenge. Arrhythmias such as ventricular tachycardia (VT), ventricular fibrillation (VF), atrial fibrillation (AF), premature ventricular contractions (PVCs), and premature atrial contractions (PACs) frequently complicate ACS, needing effective management strategies. Omega-3 fatty acids have shown potency in preventing sudden cardiac death by modulating arrhythmias, but their acute effects in ACS patients remain controversial. This study aimed to evaluate the impact of Omega-3 supplementation on reducing common arrhythmias among ACS patients. METHODS: A randomized clinical trial involving 74 ACS patients was conducted. Participants were randomly assigned to receive either 1 gr of Omega-3 daily or placebo (olive oil capsules) for five days. Arrhythmia frequencies (AF, PVCs, PACs, VT, VF) were monitored using daily ECGs, and statistical analyses were performed using SPSS software (version 24). RESULTS: Over the five days, patients receiving Omega-3 showed significant reductions in the occurrence of AF (26.66-11.66 %, p=0.015), PACs (21.66-3.33 %, p=0.043), and PVCs (36.66-3.33 %, p=0.021) compared to the control group. The frequency of VT and VF cases was low, with only one VT case in the Omega-3 group, which resolved without intervention after the second day. CONCLUSIONS: This study highlights the potential of Omega-3 fatty acids as adjunct therapy for arrhythmia management post-ACS, particularly in reducing AF, PACs, and PVCs. However, the minimal effects on VF and VT and the lack of thorough statistical analysis for these arrhythmias warrant further investigation.