PurposeThis paper aims to examine the influence of intrinsic motives (self-efficacy, reputation and reciprocity) on online knowledge sharing behaviour. Additionally, this research investigates the moderating role of individual innovation capability and top management support.Design/methodology/approachThe methodology adopted was a questionnaire survey of employees working in Vietnamese telecommunications companies. A total of 501 employees completed a self-administered anonymous survey using a cross-sectional design. Confirmatory factor analysis and ordinary least squared – based hierarchical regression was used to test the conceptual framework.FindingsSelf-efficacy, reputation and reciprocity significantly impact online knowledge sharing behaviour. Specifically, self-efficacy has an inverted U-shape association while reputation and reciprocity have a positively, returns-to-scale association with online knowledge sharing behaviour. Individual innovation capability moderates the effect on these associations as does top management support, but to a lesser extent.Research limitations/implicationsData were obtained at a single point in time and self-reported. Furthermore, this study was conducted in a specific industry in Vietnam, i.e. telecommunications, which limits the generalisability of the research.Practical implicationsOrganisations need to create a favourable environment for online knowledge sharing to foster reciprocal relationships and interpersonal interactions of employees. Encouraging and rewarding employees to actively engage in knowledge exchange will help facilitate reciprocal online knowledge sharing behaviour.Originality/valueThis study contributes to knowledge-sharing behaviour by uncovering an inverted U-shape association and positively, returns-to-scale associations between intrinsic antecedents and online knowledge sharing behaviour. Additionally, individual innovation capability was an important moderator which has been overlooked in past research.