Job burnout affects countless workers and constitutes a major issue in working life. Prevention strategies such as offering part-time options and shorter working weeks have been widely advocated to address this issue. However, the relationship between shorter work regimes and burnout risk has not yet been investigated across diverse working populations applying validated measures and frameworks for job burnout. Building on the most recent operationalisation of job burnout and the seminal job demands–resources theory, the purpose of the current study is to investigate whether shorter work regimes are associated with lower burnout risk and whether the job demands–resources explain this association. To this end, a heterogenous sample of 1006 employees representative for age and gender completed the Burnout Assessment Tool (BAT) and Workplace Stressors Assessment Questionnaire (WSAQ). Our mediation analyses yield a very small but significant indirect association between work regimes and burnout risk through job demands, but no significant total or direct association between work regimes and burnout risk. Our result suggests that employees in shorter work regimes experience slightly fewer job demands, but are equally prone to developing burnout as their full-time counterparts. The latter finding raises concerns about the sustainability of burnout prevention that focuses on mere work regimes instead of the root causes of burnout.