[2] In 2003, she moved to Vancouver to be an associate professor at the University of British Columbia (UBC) and was awarded the Canada Research Chair in Developmental Cognitive Science.

[2][4] In 2009, she joined the UC Berkeley Department of Psychology as a Professor, where she is also the director of the school's Early Learning Lab.

She worked with Susan Carey for her Ph.D. research on object individuation, sortal concepts, and early word learning.

[8] She worked with Elizabeth Spelke as a postdoctoral fellow, focusing on prelinguistic infants’ representation of numbers.

[21][22] Taking an interdisciplinary, cognitive science approach to the study of learning and development, Xu and her collaborators have developed computational models – Bayesian probabilistic models – on word learning, object perception, preference attribution, question-asking, infants' surprise, and hypothesis generation.

[28][29] She argued that human infants begin life with a set of proto-conceptual primitives such as object, number, and agent, and as young learners acquire language, these initial representations are transformed into a format that is compatible with language and propositional thought.

[30] She also suggests that infants and young children are active learners, and cognitive agency is part and parcel of development.