Background: Myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow to a part of the heart is blocked for a long enough time that part of the heart muscle is damaged or dies.The present study was conducted to assess serum sodium in acute myocardial infarction and its correlation with severity and complications of myocardial infarction. Materials & Methods: The study was conducted at Department of Medicine, Patna Medical College and Hospital, Patna during March 2023 - August 2023. 56 patients of acute myocardial infarction of both genders were divided into two groups based on the mean serum sodium value: Group I had a mean serum sodium level >135 mmol/l and group II had a mean serum sodium level ≤135 mmol/l. Results: Out of 56 patients, males were 36 and females were 20. Out of 18 patients in group I, 1 case had RVF in AWMI and 2 had biventricular failure in AWMI. Out of 38 cases in group II, 6 RVF included AWMI, 5 IWMI and 3 biventricular failures in AWMI. The difference was significant (P< 0.05). According to Killip’s classification, there were 12 patients in group I and 21 patients in group II, class II had 3 patients in group I and 8 patients in group II, class III had 1 patient in group I and 5 patients in group II and class IV had 2 patients in group I and 4 patients in group II. The difference was significant (P< 0.05). There were 1 mortality of male in group I and 7 males and 3 females in group II. The difference was significant (P< 0.05). Conclusion: Serum sodium levels are positively correlated with myocardial infarction severity, sequelae, and prognosis. Therefore, measuring blood sodium may aid in the quick evaluation of myocardial infarction severity and in the prediction of sequelae for prompt treatment.