PurposeThis study aims to investigate motivators, mediator and moderator of users' sustained information seeking on academic social networking sites (ASNSs).Design/methodology/approachDrawing upon the expectancy–value theory and related information-seeking literature, the study developed a theoretical model to explain why and how users intend to continue seeking information on ASNSs. Thereafter, a field survey with 385 participants was conducted to test the model. Finally, a content analysis of participants' post-survey feedback was performed to complement the model test results by showing more fine-grained findings.FindingsResults suggest that information usefulness and information adoption (IA) are significant to users' sustained information seeking on ASNSs, while users' satisfaction with ASNSs may play a mediating role in the relationship between information usefulness and sustained information seeking. Additionally, self-efficacy for critical thinking (SCT) weakens the impact of IA on users' satisfaction with ASNSs. The post-survey feedback analysis indicates that information usefulness is more critical to sustained information seeking for users with high SCT, whereas IA becomes more crucial to users' satisfaction with ASNSs and sustained information seeking for users with low SCT.Originality/valueAlthough the extant literature has distinguished between information seeking and sustained information seeking, empirical research into users' sustained information seeking on ASNSs is limited. The study fills this gap by proposing and validating relevant factors and the boundary condition of users' sustained information seeking.