Previous literature has indicated that perceptions of social support (PSS) may be an important predictor of parental stress levels, particularly for parents of children diagnosed with autism spectrum disorders (ASD). The current study implemented structural equation modelling to further investigate the relationship between PSS and parental stress in a sample of 454 parents of children diagnosed with ASD. Results indicate that PSS derived from friends was the most important factor in protecting against stress, with PSS from both a significant other and family appearing to be less pervasive in this regard. In addition, the importance of PSS was further underlined by the finding that it remained a significant predictor of parental stress after controlling for the absence/presence of professional support.