Evidence-based weight-loss treatments for children with autism spectrum disorder (ASD) are lacking. Therefore, a parent-based weight-loss treatment for children with ASD (PBT-ASD) was developed. A pilot study was conducted to test the initial efficacy, feasibility, and acceptability of this intervention. Parents of 20 children with ASD and overweight/obesity (mean age = 9.90 (SD = 2.31) years; 90% male; 40% Hispanic) participated in a 16-session PBT-ASD. The PBT-ASD program was found to be feasible and acceptable. Both children and parents lost weight from pre- to post-treatment (p's < 0.05). Parent-reported child physical activity and vegetable consumption increased at post-treatment (p's < 0.05). This pilot study provides a proof-of-concept for PBT-ASD. Randomized controlled trials with larger samples and follow-up are needed.