Flexible working time arrangements (FWTA) have increased over the last decades, favored by labor market deregulation, the decentralization of collective bargaining and the development of new technologies. The negative impact of some non-standard working hours on health (like night work, shift work) is quite well-known but other forms of FWTA have been studied less so far. This article aims to investigate the relationship between FWTA and workers’ health. It focuses on employer-oriented FWTA and uses a job demands-control framework to identify different types of working time demands and control. The study uses individual data from the French working conditions survey, including panel data from 2013 to 2019 (64,981 observations) and cross-sectional employer-employee linked data from 2019 (5687 employees from 4672 workplaces). We identify empirically two main dimensions of employer-oriented FWTA, based on 14 working time variables. The first type involves “atypical working hours”, such as working weekends, nights, early mornings, evenings, or doing shift work. The second type – “work overflow” – is characterized by long working hours, overtime, taking work home, and having variable working hours. Using a fixed-effects model based on panel data, we show that both types of FWTA have a negative impact on workers' self-rated general health and mental health, as measured by the WHO-5 index. The study also finds that workers who have more control – both individual and collective – to face these demands demonstrate better health. Workers with control over their working hours report better health and are less negatively affected by FWTA. Moreover, workplace-level practices have ambiguous relationships with workers' health. However, those involving social dialogue and workers’ participation have more favorable effects: the positive effect of health and safety committees is especially clear. To improve workers’ health in the context of increased flexible working time arrangements, public policies should promote the development of control over working time and participation of workers to social dialogue on working time related issues.