Early mathematical knowledge is a powerful indicator of later academic outcomes (Duncan et al., 2007), yet key findings on numerical cognition during early childhood have not been effectively translated into mathematics education (Hawes et al., 2019). Given recent teacher shortages, underfunding, and fallout from a global pandemic, it has become increasingly challenging to ask early childhood educators to add new components into already-packed days. The current study trained and supported undergraduate student volunteers to deliver a play-based numeracy intervention in preschool classrooms. The goals of this research were to (1) gain a deeper of undergraduates as novice teachers, (2) understand how and in what ways the undergraduate students were impacted by their experience in providing a play-based early numeracy intervention, and (3) assess their ability to implement a play-based numeracy intervention according to their assigned condition. Study 1 utilized repeated survey measures and written testimonies to provide a multifaceted understanding of the development of these undergraduate volunteers. We found undergraduates to be a unique population, distinct from teachers, who experienced a variety of benefits from participating in training and experiential learning. Study 2 then conducted observations to assess undergraduates' fidelity of implementation of the early numeracy intervention.The observed undergraduate students delivered high quality implementation and were able to dedicate almost all of their classroom time and attention to their students. As a whole, the current research provides preliminary evidence that undergraduate student volunteers can provide meaningful contributions to preschool classrooms in early numeracy while also learning themselves.