['To investigate whether health-related functioning mediates the effect of psychological job demands on sickness absence in nurses.', 'Nurses face high job demands that can have adverse health effects resulting in sickness absence.', 'Prospective cohort study with 1-year follow-up.', 'Data for 2964 Norwegian nurses were collected in the period 2008-2010. At baseline, psychological job demands were measured with the Demand-Control-Support Questionnaire. Health-related functioning was assessed by the Mental Composite Score and the Physical Composite Score of the SF-12 Health Survey (2nd version). Sickness absence (no = 0, yes = 1) was self-reported at 1-year follow-up. Interaction and mediation analyses were conducted stratified by tenure (<1-year, 1-2 years, 3-6 years, >6 years) as a registered nurse.', 'A total of 2180 nurses (74%) with complete data were eligible for analysis. A significant three-way interaction between job demands, control and support was found in newly licensed nurses (tenure <1-year). Baseline psychological job demands were positively associated with sickness absence at 1-year follow-up. This association was substantially weakened when Mental Composite Score and Physical Composite Score were introduced as mediator variables, indicating a partial mediation effect that was particularly pronounced in newly licensed nurses. Psychological job demands did not modify the effect of health-related functioning on sickness absence.'] Does mental and physical health-related functioning mediate between psychological job demands and sickness absence among nurses?