Noonan syndrome is a genetic disorder characterized by facial dysmorphism and several birth defects including lymphatic abnormalities. There are familial cases and sporadic cases. In practice, it is sometimes very difficult to confirm the diagnosis, as the manifestations are variable and & quot; subtle & quot; for the non-specialist. We report the case of a patient in whom the diagnosis was made late at the age of 37 years and whose reason for consultation was an increase in abdominal volume related to chylous ascites. Chylous ascites in Noonan syndrome seems to be more frequent than expected hence the need to know how to evoke this syndrome in its presence especially since there is a typical dysmorphic picture.