Background. Alar rim defects are mostly acquired, resulting from burns, traumas or tumor excision. Sometimes they can accompany craniofacial clefts. However, isolated congenital alar defects are extremely rare. Case report. We presented two cases of congenital isolated alar cleft. The defect was closed by the use of an advancement flap, the technique described by Denonvilliers. We achieved both symmetry and appropriate thickness of the nostrils. Skin color and texture of the alar rim were excellent, with scars not excessively visible. Conclusion. Denonvilliers' z-plasty technique by using advancement flap provides both functionally and aesthetically satisfying outcome in patients with congenital alar rim defects.