question: PurposeThe purpose of this study is to investigate coproduction behavior in networking alumni communities via the progress from platform belongingness, knowledge sharing and citizenship behavior. Alumni networking communities have emerged as valuable assets for conserving institutional resources, supporting members and contributing new resources for alumni-institutional professional development. However, the previous literature has not yet captured the explicit processes by which these contributions are made.Design/methodology/approachData from 711 respondents selected from an alumni collaboration network were subjected to structural equation modeling analysis.FindingsThe study explored resource conservation (belongingness) as the primary relational mechanism for alumni to share their instrumental resources (knowledge sharing), supporting resources (citizenship behavior) and competent resources (coproduction behavior). Knowledge sharing and citizenship behavior act as intermediate agents to trigger coproduction behavior. The authors show how subjective norm, group norm and trust is regarded as a tool to reduce bonding intrusiveness (i.e. the intrusive side-effects of a bond) and moderate the indirect effect of belongingness on coproduction and the direct effect of citizenship on coproduction.Research limitations/implicationsBy applying attachment theory, conservation of resources theory and digital platform networking perspectives, this study describes major implications for designing inspiring and compatible community platforms.Practical implicationsGuidance is provided for improving sustainable alumni communities through citizenship-sharing and coproduction behavior.Social implicationsOnline alumni communities are regarded as resource conservators, which can result in valuable coproduction, via the sharing of knowledge, expertise and skillsets to create profit for a range of institutions and industries.Originality/valueAlumni networking platforms encourage alumni cohesiveness, stimulate knowledge exchange and improve professionalism.