Autism spectrum disorders (ASDs) are a group of pervasive neurodevelopmental conditions characterized by social and communication deficits and rigid, repetitive patterns of behavior varying in severity. Whereas the theory-of-mind hypothesis postulates that the social shortcomings typical of these disorders stem from an impaired awareness of others’ mental states, a more recent account, the social motivation theory of autism, identifies a lack of social motivation as the cause. This study was designed to investigate the degree to which impaired social forecasting, a cardinal social deficit in ASDs, can be explained by social motivational factors, namely social orienting and the liking of social rewards, and by possible confounding variables such as social anxiety and depression. Participants (N = 93) completed an online survey assessing their autism symptomology, social motivation, social forecasting ability, and depressive and socially anxious tendencies. A Hayes mediation analysis indicated that the relationship between participants’ autism diagnosis and social forecasting performance was not significantly mediated by the social motivation variables, b = -3.21, SE = .75. However, the relationship was significantly mediated by social avoidance, b = 1.44, SE = .87, p ≤ .05. While the association between social avoidance and social forecasting ability was positive for non-autistic participants, it was negative for autistic participants. This finding could be explained by a more reactive behavioral inhibition system in autistic individuals.