•We critically reviewed the literature on cognitive development in bilingual children between 0 and 6 years of age.•Consistent findings in non-verbal executive control and theory of mind with bilinguals outperforming monolinguals, starting in the first year of life.•Inconsistent findings in metalinguistic awareness, performance influenced by factors such as language proficiency and typological distance between languages.•Memory abilities, intelligence, and processing speed received little attention and thus no firm conclusions can be drawn.•Experience with two linguistic systems, no matter how short and regardless of the language pairs involved, changes brain function. Dual language exposure and bilingualism are relatively common experiences for children. The present review set out to synthesize the existing research on cognitive development in bilingual children and to identify the gaps and the methodological concerns present in the existing research. A search of major databases for research conducted with typically developing, preschool-age dual language learners between 2000 and 2013 yielded 102 peer-reviewed articles. The existing evidence points to areas of cognitive development in bilingual children where findings are robust or inconclusive, and reveals variables that influence performance. The present review also identifies areas for future research and methodological limitations.