The renewed interest in the phenomenon of job crafting offers a promising direction for research in organizational psychology. Job crafting is a specific form of proactive work behaviour that entails changing and reshaping the tasks or relationships that make up the job in order to keep the job challenging, motivating and healthy (Demerouti, 2015; Wrzesniewski & Dutton, 2001). Recent studies have shown that job crafting can result in increased work engagement, creativity and job performance (Bakker, Tims, & Derks, 2012; Demerouti, Bakker, & Gevers, 2015; Gordon et al., 2018; Petrou, Demerouti, Peeters, Schaufeli, & Hetland, 2012; Tims, Bakker, & Derks, 2012). This is consistent with the idea that job crafting increases the fit between person and organization, as well as the meaningfulness of work. A core assumption in jobcrafting theory is that employees’ job crafting is a continuous process in which individuals can proactively change and shape the boundaries of their work (Berg, Wrzesniewski, & Dutton, 2010) e from day to day. Thus, several beneficial outcomes of job crafting have been demonstrated using within-person designs that capture the day-to-day dynamics of job crafting and illuminate its positive short-time outcomes for individual employees (e.g. Petrou et al., 2012; Tims, Bakker, & Derks, 2014). Despite these promising findings, the job-crafting literature is still in its infancy. Among the unresolved questions is the question of what role leaders play in the job-crafting process? The lack of attention to the role of the leader in the job-crafting process is surprising given that the link between leadership and other forms of self-initiated proactivity at work is well established, both theoretically and empirically, in the general literature on proactive workplace behaviour (e.g. Den Hartog & Belschak, 2012; Schmitt, Den Hartog, & Belschak, 2016). More specifically, research on proactive work behaviour suggests and demonstrates that transformational leadership in particular plays a key role in explaining both individual-level (Den Hartog & Belschak, 2012; Schmitt et al., 2016) and team-level proactivity (Strauss, Griffin, & Rafferty, 2009). However, one limitation of this line of research is that it uses research designs that focus strictly on between-person or between- team variances. Consequently, it may fail to take into account shortterm, intra-individual variances in the leadership-proactivity relationship. In the present study, we argue that leader perceptions and job-crafting behaviour are likely to vary from one day to the next. Therefore, in addition to using more conventional research designs, we need to use quantitative diary designs to capture these day-today dynamics. Compared to cross-sectional or longitudinal designs with time lags of several months or even years, diary methods are useful because they capture the short-term dynamics of experiences within and between individuals in the work context (Ohly, Sonnentag, Niessen, & Zapf, 2010). In this light, the present study aims to expand existing knowledge by being one of the first studies to examine the important link between transformational leadership and proactive work behaviour in the form of job crafting. It does so by applying a quantitative diary design over a period of five days in a field context, contributing new knowledge about the dayto-day dynamics of the relationship between leadership and employee proactivity at work.