This study puts forward a novel advancement on understanding the underlying mechanisms that expound how human capital can lead to employees” innovative behaviour. Thus, this study intends to examine the nuanced associations between human capital and innovative work behaviour, evoking the mediation of employee engagement and moderation of mental involvement. Utilising a cross sectional research design, a random-sampling technique was used to collect responses from professionals selected from different organizations operating in Jordan. In total, 380 participants completed a questionnaire constructed from well-established measures. AMOS-Structural Equation Modelling was used to examine the measurement and structural models. The results demonstrated that, along with the direct effect, human capital asserts a substantial relevance to individuals” innovative behaviour via the mediation of employee engagement and moderation of mental involvement. To the best of the researcher’s knowledge, this is the first research attempt that views the aforementioned associations through the lens of the attitudinal constructs of employee engagement (mediator) and mental involvement (moderator). Further, this study expands the knowledge base of the cognitive, attitudinal, and behavioural literature by expanding the scope of the JD-R theory aspects to be linked to other psychological dynamics (employee engagement and mental involvement) thought to enhance employees” innovative behaviours.