Cystic fibrosis (CF) is a progressive, genetic disease that causes persistent lung infections and limits the ability to breathe over time. Even though more than 1000 mutations have been identified in the cystic fibrosis transmembrane regulator (CFTR) gene, the data from India is limited. Facilities for diagnosis of CF is not easily available across various parts of India even today. A 3 months old male infant presented with severe metabolic alkalosis, hyponatremia and hypokalemia to our hospital with failure to thrive. The clinical presentation was similar to that of Bartter’s syndrome and a diagnosis of CF was confirmed only through genetic analysis with mutations of compound heterozygosity c.1029delC (p.C343) in exon 8 and c.335C>T (p.S1118F) in exon 20 of CFTR gene.