The most significant challenge in facilitating a professional virtual community (PVC) is maintaining a continuous supply of knowledge from members, especially because lurkers often make up a large portion of an online community. However, we still do not understand how knowledge‐sharing intention (KSI) is formed across poster and lurker groups. Accordingly, this study seeks to provide a fuller understanding of the formation of behavioral intention in PVCs by decomposing the psychological formation of KSI and focusing on factors deemed likely to influence the KSI of posters and lurkers. This study's online survey of 177 posters and 246 lurkers from 3 PVCs demonstrated that enjoyment in helping others positively influenced posters' attitudes toward knowledge sharing, whereas reciprocity and technology adoption variables (perceived ease of use and compatibility) positively influenced lurkers' attitudes. Interpersonal trust and peer influence strongly affected the subjective norm of knowledge sharing in both groups, with posters emphasizing interpersonal trust and lurkers emphasizing peer influence. Furthermore, knowledge self‐efficacy and resource availability enhanced the perceived behavioral control of knowledge sharing in both groups, with knowledge self‐efficacy affecting posters the most and resource availability influencing lurkers the most. The results of this study have important implications for both research and practice.