Positive employee attitudes and behaviours arise when employees perceive that they are compatible with their jobs, known as person-job (PJ) fit (Kristof-Brown et al., 2005). Yet, to date, relatively few studies have examined the antecedents of PJ fit perceptions and their dynamic nature (e.g., Bayl-Smith & Griffin, 2018; De Cooman et al., 2019). In particular, little is known about the proactive role that employees may play in the development of these perceptions. Although scholars have proposed that a lack of PJ fit may trigger job crafting behaviours aimed at improving PJ fit (Tims & Bakker, 2010), more research is needed to test this proposition. Approaching PJ fit as both perceived needs-supplies (NS) fit and demands-abilities (DA) fit, the present research contributes to testing this proposition and develops theoretical arguments about the differential impact of these types of fit on job crafting behaviours, based on conservation of resources theory (Hobfoll, 1989). In so doing, approach and avoidance crafting behaviours are distinguished (Zhang & Parker, 2019). In addition, the interaction between perceived NS fit and DA fit in predicting job crafting behaviours is proposed and tested. Using a threemonth time-lag study design, hypotheses were tested using 492 participants from a heterogeneous group of US workers. Results from structural equation modelling showed that perceived DA fit negatively affected approach and avoidance crafting behaviours, while perceived NS fit facilitated approach crafting behaviours. Perceived NS fit strengthened the effect of perceived DA fit on job crafting behaviours. In addition, approach crafting behaviours facilitated a positive change in PJ fit perceptions, while avoidance crafting behaviours hindered this development. Overall, findings suggest that PJ fit perceptions might change through job crafting behaviours over time. The theoretical and practical implications of these findings are discussed and scholars are encouraged to carry out further research to assess their generalisability.