Organisations invest in human capital to achieve favourable organisational performance. The purpose of this research is to explain how organisational human capital investments influence an individual’s human capital and innovative work behaviour (IWB). Drawing on Social Exchange Theory and its subset Affect Theory of Social Exchange, this study empirically examines how the human resource management activity of human capital investments manifests at the individual level by developing and testing a moderated serial mediation model. A total of 115 employees working in a diverse set of industries, such as service, manufacturing, information technology, consultancy and education, who had received at least one training from their current employer, participated in the survey. The participants completed five standardized, valid and reliable instruments. SPSS was employed for data analysis. Hypotheses were tested using regression analysis. Results show that both gratitude and knowledge management mediate the relationship between human capital and IWB and the moderating effects of job characteristics. This study extends current literature and integrates macro–micro human capital by exploring how and when human capital leads to the generation of micro social orders. The concept of micro social orders refers to repeated interactions (exchange frequency), emotional reactions, perceptions of cohesion and affective sentiments of a group/organisation due to social structures. This research also highlights how managers can establish positive reciprocity obligations and enhance employees’ gratitude that helps to achieve IWB.