Background: Inferior myocardial infarction (MI) often results from right coronary artery (RCA) occlusion, with lesion location affecting infarct severity and outcomes. ST-segment elevation is a key prognostic marker, but its relationship with RCA lesion sites remains underexplored, particularly in Bangladesh. This study investigates the association between ST-segment elevation magnitude and RCA lesion sites (proximal, mid, and distal) and their impact on in-hospital complications. Methods and Materials: This observational study at the National Institute of Cardiovascular Diseases (NICVD), Bangladesh, included 100 acute inferior MI patients. RCA lesions were classified via coronary angiography. Electrocardiographic parameters, in-hospital complications, and echocardiographic findings were analyzed using chi-square and ANOVA tests (p < 0.05). Results: Proximal RCA lesions were associated with significantly greater ST-segment elevation in leads II, III, and aVF (p < 0.001) and higher prevalence of right ventricular involvement (p < 0.001). Patients with proximal lesions had a significantly higher incidence of hypotension (75.0%, p < 0.001), cardiogenic shock (27.1%, p = 0.012), acute left ventricular failure (45.8%, p < 0.001), and arrhythmias (39.6%, p = 0.005). Echocardiographic findings showed greater regional wall motion abnormalities in proximal lesions (p < 0.001), while left ventricular ejection fraction differences were not statistically significant (p = 0.060). Conclusion: Proximal RCA lesions are associated with more extensive ST-segment elevation and worse in-hospital outcomes, highlighting their prognostic significance. These findings emphasize the importance of lesion site identification for early risk stratification and tailored management strategies in acute inferior MI.