PurposeCrowdsourcing communities enable companies to post challenges that are completed by solvers (workers); their success depends on engagement, requiring both creativity and effort. This study explores solver engagement in online crowdsourcing communities, advancing the theory of trait engagement by investigating the mediating roles of: (a) task-related self-efficacy in linking conscientiousness, neuroticism and extraversion, with solver engagement, and (b) task complexity in influencing the mediation.Design/methodology/approach215 valid responses were obtained from solvers engaged in the popular Chinese crowdsourcing community, Epwk.com, using an online questionnaire. PLS was then used to analyze the data.FindingsResults show that self-efficacy mediates the relationships for conscientiousness, neuroticism and extraversion, with solver engagement. Moderated mediation analysis revealed that self-efficacy mediates the relationships for: (a) conscientiousness and extraversion, for only solvers with high task complexity; and (b) neuroticism, for only solvers with low task complexity.Originality/valueThe authors’ findings underscore the importance of accounting for solvers' situational contexts when examining the relationships between personality, self-efficacy and solver engagement in online crowdsourcing communities.