In France, 17 % of employees are currently concerned by shift-work. For a better understanding of the psychological effects of shift-work, we evaluated the extent to which perceptions of the job environment vary according to the shift worked, and to the shift-phase. A self-administered questionnaire was elaborated to measure job perceptions of 14 caregivers and 24 nurses (86 observations). In reference to the Job Content Questionnaire (JCQ, Karasek et al., 1998), the questionnaire addressed psychological and physical demands, control, supervisor and co-worker social support, and two additional dimensions: availability of technical and human resources and work-family interferences. Each participant completed the questionnaire three times (one hour after shift-beginning, in the middle of the shift, one hour before shift-end) on each shift worked (morning- shift, afternoon-shift and night-shift). Results indicated overall higher psychological demands at the beginning and in the middle of the shift than at the shift-end, and higher physical demands at the shift-end. Further, on the night-shift compared to the morning- and afternoon-shifts, the perception of autonomy was higher, while social support by co-workers was lower. These main effects were qualified by an interaction between shift and shift-phase: co-worker support and availability of technical and human resources increased across the morning-shift, decreased across the afternoon-shift and remained stable during the night-shift. Together with the results concerning perceived job demands, these results indicate that during the night shift, participants were less exposed to job strain, especially in the middle of the shift. During the morning-shift, job perceptions indicated positive stress in the middle of the shift and low tension at the shift-end, whereas during the afternoon-shift the professional tension increased throughout the shift. Thus, a differential assessment of job perceptions according to the shift and shift-phase is important in order to assess perceived workload that would be determined by both psychological and physical job demands in healthcare staff. Our findings also highlight the importance of introducing the dimension of technical and human resources in addition to social support and control, in agreement with the “job demands-resources” model (JD-R; Demerouti et al., 2001). Even though these results may not be extended to other job situations, and need to be interpreted in light of task organization across the 24-h day in this job-situation, the methodology provides complementary information to the more general approach of job perceptions.