Abstract Background Perinatally chikungunya infected neonates have been reported to have high rates of post-infection neurologic sequelae, mainly cognitive problems. In older children and adults chikungunya does not appear to have sequelae, but data on postnatally infected infants are lacking. Methods We performed a prospective, non-controlled, observational study of infants infected before the age of 6 months with a severe chikungunya infection during the 2014–2015 epidemic in Curaçao, Dutch Antilles. Two years post-infection cognitive and motor - (BSID-III) and social emotional assessments (ITSEA) were performed. Results Of twenty-two infected infants, two died and two were lost to follow up. Eighteen children were seen at follow-up and included in the current study. Of these, 13 (72%) had abnormal scores on the BSID-III (cognitive/motor) or ITSEA. Conclusion In the first study aimed at postnatally infected infants, using an uncontrolled design, we observed a very high percentage of developmental problems. Further studies are needed to assess causality, however until these data are available preventive measure during outbreaks should also include young infants. Those that have been infected in early infancy should receive follow up.