• webbed and short appearing neck
• sternum abnormalities (pectus excavatum, occasionally pectus carinatum)
• sagging eyelids (ptosis)
• wide-set (hypertelorism) or down-slanting eyes
• low-set or abnormally shaped ears
• undescended testicles
• delayed puberty
• mental retardation in only a quarter of patients
• short stature
• small penis

Examination may show an extra fold of skin above the eyes (epicanthal folds). The eyes may also appear down-slanted (antimongoloid palpebral slant). The arms may be held at an unusual angle (cubitus valgus). There may be signs of congenital heart disease (often pulmonic stenosis, occasionally ASD). There may be a bleeding tendency revealed by low platelet count or coagulation tests and measuring the levels of specific coagulation factors in the blood (factors XI-XIII).

Testing will depend on the symptoms present. For example, if there are signs of heart disease, an ECG, chest X-ray or echocardiogram may be recommended. Hearing tests are indicated if there is any sign of decreased hearing.

Genetic testing has two purposes. First, a karyotype analysis can make sure that no easily detected abnormality of chromosomes can be mistaken for Noonan syndrome. Second, research genetic testing for mutations in the PTPN11 gene may be available.