Introduction: Cystic fibrosis is increasingly recognized in Sri Lanka, where atypical early presentations may contribute to delayed diagnosis. Pseudo-Bartter syndrome, defined by hypochloremic metabolic alkalosis with hyponatremia and hypokalemia, together with vitamin K deficiency–related coagulopathy , is an uncommon but important initial manifestation of the disease in infancy . Case presentation: A three-month-old previously healthy boy presented with a one-week history of recurrent vomiting, fever, and generalized echymotic patches. He was the third child of non-consanguineous parents with two healthy older siblings, and his growth had been appropriate at the time of presentation. Physical examination was unremarkable except forwidespread ecchymosis. Laboratory investigations demonstrated hypochloremic metabolic alkalosis (pH 7 .50, HCO₃? 30 mmol/L, serum chloride 77 mmol/L), hyponatremia (127 mmol/L), and hypokalemia (2.4 mmol/L). Urinary electrolytes were markedly low , consistent with extra-renal salt loss. Coagulation studies revealed prolonged PT/INR and APTT, which corrected followingintravenous vitamin K and fresh frozen plasma. The urine calcium-creatinine ratio was normal. Radiological evaluation excluded nephrocalcinosis, pyloric stenosis, and intestinal malrotation.Stool microscopy showed numerous fat globules. A sweat chloride concentration of 103 mmol/L confirmed the diagnosis of Cystic fibrosis. Genetic analysis is pending. He was discharged on Na and K supplements, pancreatic enzyme replacemnet and fat soluble Vitamins. Conclusion: Pseudo-Bartter syndrome with vitamin K deficiency–related coagulopathy may be the sole presenting manifestation of this condition in early infancy , even without respiratory or obvious gastrointestinal involvement. Maintaining a high index of suspicion is essential to enable timely diagnosis and management in emerging patient populations in Sri Lanka.