•Individual employees’ knowledge hiding behaviors have two-side effects on the firm’s innovation quality.•There is an inverted U-shape relationship between the explicit knowledge hiding and the firm’s innovation quality.•There is an inverted U-shape relationship between the tacit knowledge hiding and the firm’s innovation quality.•Knowledge flow within the firm positively moderate the curvilinear relationships between knowledge hiding and the firm’s innovation quality. This study explores how two dimensions of employees’ knowledge-hiding behaviours, explicit knowledge hiding and tacit knowledge hiding, influence a firm’s innovation quality. Furthermore, knowledge flow within the firm is examined as a moderator in these relationships. We tested corresponding hypotheses based on a research sample of 791 respondents across different industries and regions of China. Empirical results reveal that both explicit and tacit knowledge-hiding behaviours have inverted U-shaped relationships with innovation quality, and knowledge flow within the firm positively moderates these curvilinear relationships. The theoretical contributions of the study are to provide a more advanced understanding of the link between knowledge-hiding behaviours and innovation quality, as well as the role of knowledge flow within the firm. It is therefore suggested that practitioners encourage effective knowledge flow that helps to reduce individual employees’ intentions of knowledge hiding and strengthen their innovation capability, which in turn promotes a firm’s innovation quality.