PurposeMobile messaging groups (MMGs) have been widely adopted in construction practice, yet, little is known about how to foster knowledge sharing (KS) in MMGs, characterized by communication visibility. This study is thus motivated to investigate mechanisms for KS in this context.Design/methodology/approachThe paper employs knowledge governance theory to construct a theoretical model and develop hypotheses. Specifically, psychological safety is identified as a mediator between knowledge governance mechanism (KGM) and KS, and promotion regulatory focus is identified as a moderator between KGM and psychological safety. Data from 208 Chinese construction project team members are collected to test the proposed theoretical model.FindingsThe results suggest that both formal and informal KGM positively affect psychological safety, which in turn improves KS (quantity and quality). Moreover, the mediating role of psychological safety is confirmed, and the moderating role of promotion regulatory focus is validated.Originality/valueThis study explores how to foster KS in MMGs, which are pervasive in today’s digital age. The findings in this study enhance the understanding of KS in digital environments and afford important insights into knowledge management within construction project teams.