Cystic fibrosis (CF) is an autosomal recessive disease that is very rare in Asians: only a few cases have been reported in Korea. We treated a female infant with CF who had steatorrhea and failure to thrive. Her sweat chloride concentration was 102.0 mM/L. Genetic analysis identified two novel mutations including a splice site mutation (c.1766+2T >C) and a frameshift mutation (c.3908dupA; Asn1303LysfsX6). Pancreatic enzyme replacement and fat-soluble vitamin supplementation enabled the patient to get a catch-up growth. This is the first report of a Korean patient with CF demonstrating pancreatic insufficiency. CF should therefore be considered in the differential diagnosis of infants with steatorrhea and failure to thrive.