Background: Teachers and clinicians may struggle to provide early identification to support multilingual children's language development. Dynamic assessments are a promising approach to identify and support children's language development. Aims: We developed and studied a novel word learning task that is dynamic and language neutral. It makes use of multilingual children's abilities to apply language transfer, fast mapping and socially embedded language to the learning of new words. Methods & Procedures: A total of 26 children attending kindergarten in French participated in this study. Within this group, 13 different home languages were spoken. Children took part in a dynamic assessment task of their word learning that consisted of a test-teach-retest task. Children's scores on this task were compared with their language abilities reported by their parents, amount of language exposure and scores on standardized tests of vocabulary. All tasks were delivered in French. Outcomes & Results: Children had higher accuracy for known words as compared with new words in the task, which may suggest transfer of knowledge from their first language. They also showed increased accuracy in identifying and naming the new words across the three trials, suggesting fast mapping of these new vocabulary items. Finally, the scores on the dynamic task correlated to children's vocabulary scores on the standardized tests, but not parent report of language development, or the amount of exposure to the language of school. Conclusions & Implications: This novel dynamic assessment task taps into the process of vocabulary learning, but is less influenced by prior language knowledge. Together, these findings provide insight into early word learning by young multilingual children and proposes a conceptual model for identifying strategies to support second language acquisition.