Congenital pulmonary airway malformation (CPAM), previously known as congenital cystic adenomatoid malformation (CCAM), is a rare developmental lung abnormality with the potential for malignant transformation. Bronchioloalveolar carcinoma (BAC), pleuropulmonary blastoma (PPB), rhabdomyomatous dysplasia/rhabdomyosarcoma (RMS) have been associated with CPAM. We report an unusual case of a 1-day-old male newborn who underwent lobectomy for a cystic lung lesion, which was found to be a mucinous BAC with K-ras mutation in a type 1 CPAM. The case supports the relationship between type 1 CPAM and BAC/KRAS mutant, and highlights that the malignant transformation can occur in very early stage of the infancy.