In this pilot study, we tested the effects of a novel intervention (JASPER, Joint Attention Symbolic Play Engagement and Regulation) on 3 to 5 year old, minimally verbal children with autism who were attending a non-public preschool. Participants were randomized to a control group (treatment as usual, 30 h of ABA-based therapy per week) or a treatment group (substitution of 30 min of JASPER treatment, twice weekly during their regular program). A baseline of 12 weeks in which no changes were noted in core deficits was followed by 12 weeks of intervention for children randomized to the JASPER treatment. Participants in the treatment group demonstrated greater play diversity on a standardized assessment. Effects also generalized to the classroom, where participants in the treatment group initiated more gestures and spent less time unengaged. These results provide further support that even brief, targeted interventions on joint attention and play can improve core deficits in minimally verbal children with ASD.