Objective: The purpose of the present study was to examine motivation for the contextual nature of motivations for social participation in cognitively able adolescents and adults with autism spectrum disorder, using self-determination theory as a theoretical framework. Methods: Fourteen Australians and 16 Taiwanese (aged 16-45 years) with Asperger’s syndrome and high functioning autism were asked to carry a device which prompted them seven times/day for 7 days, to record what they were doing, with whom, perceived difficulty and social reciprocity, and the reasons for engaging in a situation, which were then coded into degree of self-determination. Results: Multilevel analyses showed that participants were more likely to be self-determined while engaging in “solitary/parallel leisure” and “social activities” than in other types of activities. Interactions with “family members” and “casual/intimate friends” were also positively associated with self-determined motivation. Further, participants were more likely to perceive higher levels of being listened to during interaction with casual/intimate friends than in interaction with other people. Global social anxiety served as a moderator for their perceptions of difficulty and social reciprocity during social engagement. Conclusion: The findings highlight the context-dependent motivations for social engagement of cognitively able individuals with autism spectrum disorder.