Fanconi-Bickel syndrome is a metabolic disease caused by mutations in SCL2A2 gene. Hepatic and renal glycogen storage, fasting hypoglycemia, and renal tubular dysfunction are characteristics of the disease that is usually diagnosed at 6-10 months of age. Here, we present a case of Fanconi-Bickel syndrome in a patient who was diagnosed at 47 days of age with the findings of glycosuria, hyperglycemia and an elevated level of alkaline phosphatase (ALP). The diagnosis was confirmed by identification of a new mutation in SLC2A2 gene and metabolic control was provided by a galactose-restricted high protein diet. A 27-day-old female patient was admitted with glycosuria. It was observed that she did not gain enough weight, had fat cheeks and hepatomegaly. Biochemical investigations revealed transaminase and ALP elevation. Fasting plasma glucose level was normal whereas postprandial glucose level was 198 mg/dL Urinalysis revealed 1+ protein and 3+ glucose. In follow-up, hyperglycemia started to be more evident, the ALP level decreased, compensated metabolic acidosis developed and the diagnosis of Fanconi-Bickel syndrome was assumed at 47 days of age. Under nutrition and oral replacement therapies good metabolic control and weight gain could be achieved. Postprandial hyperglycemia and glycosuria are early diagnostic clues for Fanconi-Bickel syndrome. Awareness of early findings and initiation of galactose-restricted high protein diet may provide metabolic control and prevent late complications.