A social skills training has previously resulted in positive improvements in social skills among children and adolescents with autism spectrum disorder (ASD). This pilot study developed a play-based social skills training protocol for first-grade elementary children with ASD in Taiwan and determined its efficacy. Using a single-group pretest-posttest design, this study recruited seven first-grade elementary children with ASD aged 6-7 years. Seven children enrolled in a regular classroom participated in a 12-week play-based social skills training program which was led by an occupational therapist. The improvement of social skills was evaluated by occupational therapists through video coding and goal attainment scales. Caregivers and teachers were asked to complete the communication and socialization domains of the Vineland Adaptive Behavior Scale-Third Edition. The results showed significant improvements in the children's social skills performance between the pretest and posttest based on video coding and goal attainment scale. Significant improvements in the Vineland Adaptive Behavior Scale-Third Edition growth scale values of receptive and written language subdomains were observed. This study established an intervention protocol for first-grade children with ASD that could be used as a guide by clinical professionals who work with children with ASD who experience problems adapting to elementary school.