BackgroundWhether preschool children with autism spectrum disorder (ASD) have motivation for social engagement is a matter of great concern. However, the current findings derived in laboratory settings are still controversial, probably because the motivation for social engagement depends on the specific social contexts. Therefore, we compared the motivation for real-life social engagement between preschool children with ASD and typically developing (TD) peers from the caregivers’ perspectives using the self-determination theory (SDT) and experience sampling methodology (ESM). The SDT helped us to examine the impact of living contexts on the motivation for social engagement, and the ESM allowed us to record objective and subjective experiences in real time across natural settings. MethodThirty preschool children with ASD and 30 matched TD peers were recruited. Caregivers carried mobile devices to record their children’s social experiences repeatedly over seven days. Multilevel modelling was used for analysis. ResultsRegardless of ASD, preschool children were more likely to be autonomous and intrinsically motivated while engaging in social play/leisure activities, but less likely to be autonomous, competent, and intrinsically motivated in non-play/leisure activities involving social interactions. The ASD group was also less likely to care about others or to be cared about in social play/leisure activities. ConclusionsThe findings highlight that the motivation for social engagement in preschool children with ASD is situation-specific and emphasize the importance of providing a supportive environment and encouraging engagement in social play/leisure activities.