The aim of the study was to assess various aspects of visual and visuoperceptual function in patients with Noonan syndrome (NS) or LEOPARD syndrome (LS) with mutations affecting the PTPN11, SOS1 and RAF1 genes. Twenty-four patients were assessed with a battery of tests assessing visual function including ophthalmological and orthoptic evaluation and age appropriate behavioural visual tests, including measures of crowding acuity (Cambridge crowding cards), and stereopsis (TNO test). Twenty-one subjects were also assessed with the visuo-motor integration (VMI) test. Twenty of the 24 patients (83%) had abnormalities of visual function on at least one of the tests used to assess visual function or on ophthalmological examination, and 7 of 21 (33%) also had abnormalities on VMI. Ocular movements and stereopsis were most frequently abnormal (50% and 79%, respectively). Our results suggest that visual and visuoperceptual abilities are commonly impaired in patients with Noonan and LEOPARD syndrome and they are probably related to a multifactorial etiology.