Children with neurofibromatosis-1 (NF1), a neurodevelopmental disorder resulting from a mutation of the NF1 gene (17q11.2), often have difficulties with learning and attention, but there is little research in the early childhood years. In this study, the cognitive and psychosocial functioning of 40 young children with NF1 (ages 3 through 6) was examined and compared both to normative data and to a contrast group comprised of unaffected siblings and community members matched for age and socio-economic status (n = 37). Children with NF1 showed significantly weaker cognitive abilities across all domains and for the vast majority of subtests. Consistent with research in older children, a variety of patterns of intra-individual strength and weakness were present for young children with NF1. Few significant group differences in psychosocial functioning were observed, but the children with NF1 showed significantly greater functional communication problems than did the unaffected group. Overall, the results indicate that in participant groups matched for age and socioeconomic status, cognitive vulnerabilities are evident for close to half of young children with NF1, with some relations to psychosocial functioning, particularly functional communication, attention problems and social skills.