Purpose: A common goal of peer-mediated interventions is to train peers to successfully initiate and maintain social and linguistic interactions with a target child in the classroom. Ample evidence indicates that peer-mediated interventions improve social and linguistic outcomes for students in the primary and later grades with developmental disabilities; however, relatively little work has focused on applying these approaches to socially isolated preschoolers who are vulnerable to academic and social challenges. In this early-stage feasibility study, we examined the potential of Promoting Early Engagement, Relationships, and Socialization (PEERS), a peer-mediated intervention designed to support socially isolated preschoolers. The main goal was to consider whether the intervention showed promise for improving the social and linguistic experiences of young, isolated children and was appropriate for implementation in a preschool setting. Method: In one preschool classroom, two peers who were well connected to their classmates were trained via storybook-based activities to provide social support to an isolated classmate. In-person and sensing technology observations were used to examine the target student's incoming peer interactions, outgoing peer interactions, and physical proximity to peers. Results: In-person observations showed a trend toward increased interactions; sensing technology data, which provided longer snapshots of classroom experiences, were more variable. In addition, teachers perceived PEERS to be appropriate and effective. Conclusion: The findings of this study support further investigation of storybook-based peer-mediated interventions in preschool settings to improve the social and linguistic experiences of children who are socially isolated.