Development of professional competencies is a key outcome of undergraduate programs preparing practitioners to work with infants and toddlers. Competencies for working with young children were examined among 1300 undergraduate students at 12 universities. Students completed a series of online questionnaires indicating their knowledge, beliefs, and hypothetical practices with young children; end-of-semester scores were analyzed using linear regression. Having had a practicum course is associated with more positive dispositions for supporting the development of teacher-child relationships, building partnerships with diverse families, guiding children's behavior, and fostering development and learning. Further, we examined development of dispositions over the course of a semester based on undergraduates' current and past practicum experiences. Implications for programs who prepare infant and toddler practitioners are discussed.