Background Healthcare workers in nursing homes are faced with high job demands that can have a detrimental impact on job-related outcomes, such as job satisfaction. Job resources may have a buffering role on this relationship. The Demand-Control-Support (DCS) Model offers a theoretical framework to study how specific job resources can buffer the adverse effects of high demands, and can even activate positive consequences of high demands. Objectives The present study tests the moderating (i.e. buffering and activating) effects of decision authority and coworker- and supervisor support that are assumed by the hypotheses of the DCS Model. Design A national cross-sectional survey was conducted with an anonymous questionnaire. Setting One hundred and thirty six living arrangements that provide nursing home care for people with dementia in the Netherlands. Participants Fifteen healthcare workers per living arrangement. In total, 1147 people filled out the questionnaires (59% response rate). Methods Hierarchical multilevel regression analyses were conducted to test the assumption that the effect of job demands on the dependent variables is buffered or activated the most when both decision authority and social support are high. This moderation is statistically represented by three-way interactions (i.e. demands × authority × support), while lower-order effects are taken into account (i.e. two-way interactions). The hypotheses are supported when three-way interaction effects are found in the expected direction. The dependent variables studied are job satisfaction, emotional exhaustion, and personal accomplishment. Results The proposed buffering and activation hypotheses of the DCS Model were not supported in our study. Three-way interaction effects were found for emotional exhaustion and personal accomplishment, though not in the expected direction. In addition, two-way interaction effects were found for job satisfaction and emotional exhaustion. Decision authority was found to buffer the adverse effect of job demands and to activate healthcare staff. Supervisor support was found to buffer the adverse effect of job demands on emotional exhaustion in situations with low decision authority. Finally, coworker support was found to have an adverse effect on personal accomplishment in high strain situations. Conclusions Findings reveal that decision authority in particular makes healthcare workers in nursing homes less vulnerable to adverse effects of high job demands, and promotes positive consequences of work.