Objectives: Acute cardiorenal syndrome (CRS type-1) refers to an acute worsening of heart function, leading to acute kidney injury (AKI), frequently complicating acute decompensated heart failure (ADHF). This study aims to investigate whether hyponatremia, is a surrogate marker for the development of AKI in patients admitted with ADHF. Materials and Methods: Sample size – 100 patients with ADHF. Age – More than 18 years. Investigations – 2D-ECHO, N-terminal pro-brain natriuretic peptide, kidney function test, estimated glomerular filtration rate, USG abdomen, complete blood picture, chest X-ray, and complete urine examination. Results: On analysis of data, 63.5% (n=33) of patients who had hyponatremia (n=45) eventually developed AKI during hospital stay, whereas 36.5% (n=19) of patients who did not have hyponatremia (n=36) developed AKI. Hyponatremia was found to be a statistically significant (P = 0.001) predictor of increased incidence of AKI in a predetermined group of patients with HF in our study, and ADHF patients with hyponatremia have a 5.21-fold higher risk of developing AKI (95% CI, 2.20–12.36) than ADHF patients without hyponatremia. Conclusion: Hyponatremia predicts complications while admission in heart failure patients like type-I CRS and it has also been shown that comorbidities could play an important role in the presence or absence of hyponatremia and could even influence the length of hospital stay attributed to lower serum sodium levels which need further clinical trials.