The Four-Day Work Week (FDWW) is gaining popularity among businesses and the public in the United Kingdom (UK), driven by optimistic indicators (e.g. increased business productivity) from the six-month FDWW trial (the trial) (4 DAY WEEK GLOBAL, 2022). FDWW based on the ‘100:80:100 principle’ is in its infancy (i.e. 80% of working time and 100% salary in return for maintaining 100% productivity); evidence on its impact remains scarce, especially regarding its shortcomings. Though FDWW offers workers more time for leisure without impairing earning capacity (Kallis et al., 2013), it leads to tighter schedules for workers (CITYA.M., 2022). Time pressure can then reinforce occupational stress for workers (Demerouti et al., 2001), especially for older workers normally perceived as less adaptable (Van Dalen et al., 2010; Rix, 2001). However, no previous study has investigated the impact of FDWW on older workers (Bird, 2009). Such research gaps should be filled for their significance to three issues today: equality, healthy ageing and economic recovery. This study therefore explores whether FDWW imposes occupational stress on older workers through sequential explanatory approach.