Parents of children with autism spectrum disorders (ASD) often are faced with the challenges of difficult parenting situations. We explored the effectiveness of the Stepping Stones Triple P (SSTP) group parent training as an additional intervention in the treatment of ASD. Parents (n = 23) went through a waiting period and participated afterwards in the training program. We assessed parenting variables via self-report measures. After the intervention, there was a significant reduction of over-reactive parenting behaviors, role restriction and an increase in parental self-efficacy. At follow-up, the effects remained stable and we additionally found a reduction of laxness and less parenting stress. Effect sizes were high (η2: 0.18–0.24). The SSTP, offered as an additional intervention in the treatment of ASD, proved to be effective in enhancing parenting.