Children's language background relates to their neurocognitive development. Knowledge of this relationship is important as bilingualism is common. However, research regarding language background in relation to performance on cognitive tests such as the WPPSI-IV and NEPSY-II is scarce. The present study compared WPPSI-IV and NEPSY-II performances between 5- and 6-year-old Swedish-speaking monolingual (n = 45) and Swedish-Finnish-speaking simultaneous bilingual (n = 34) children in Finland. The participants were gathered by stratified sampling and were assessed with the Swedish versions of the tests. In profile analyses, a significant monolingual advantage was found in some WPPSI-IV subtests and indexes requiring expressive vocabulary (Vocabulary, Similarities, Picture Naming, and Vocabulary Acquisition Index) and visuospatial skills (Object Assembly and Visual Spatial Index). No group differences were found between mono- and bilingual children in receptive language, visual memory, or fluid intelligence. Additionally, no differences were found on the Full Scale IQ. The performance on the WPPSI-IV Similarities subtest improved in a subgroup of bilinguals when answers in both Swedish and Finnish were accounted for, instead of accepting only answers in Swedish. No significant differences were found between mono- and bilinguals on the language and memory tasks of NEPSY-II. These findings highlight the importance of considering the child's language background when assessing expressive language in young children, as well as the benefits of assessing bilinguals in both of their languages.