A stream of research studies examined the effects of financial knowledge on financial well-being. However, the mediating role of financial attitude and financial behaviour in this relationship needs to be explored. In this backdrop, the objective of the study is to examine the effect of financial knowledge on financial well-being considering the mediating effect of financial attitude and financial behaviour in this relationship. The study has used a secondary dataset of 47,132 households from the Financial Inclusion Insight database. Apart from basic statistical tools, serial mediation analysis is employed to explore the mediating role of financial attitude and financial behaviour in this relationship between financial knowledge and financial well-being. The study’s outcome confirmed the direct positive effect of financial knowledge on financial well-being as well as the favourable indirect effect through the mediating factors (i.e., financial attitude and financial behaviour). However, the cumulative indirect effect of financial knowledge on financial behaviour is greater than the direct impact. Moreover, among the mediators, financial attitude serves as the most significant channel, whereas financial behaviour has a minimal contribution. This demonstrates that, even in the absence of substantial behavioural changes, cultivating favourable financial attitudes by increasing optimism and confidence and lowering financial stress can greatly enhance perceived financial stability and happiness. Therefore, it is necessary to focus not just on financial knowledge (i.e., the cognitive aspect) but also on the psychological aspects of individual to ensure financial well-being.