Objective: The present study examined the effects of caregiving stress and ageing on neutrophil function in young and older individuals. Design: As a model of caregiving, young parents (aged 38.3 +/- 4.78) of children with developmental disabilities were recruited and compared to older caregivers (aged 70 +/- 6.03), full time carers of a spouse with dementia. Age- and gender-matched controls were also assessed. Methods: Participants completed a questionnaire pack assessing health behaviours, psychosocial status and caregiving characteristics, and provided a blood sample for assay of neutrophil function (phagocytosis of Escherichia coli and generation of reactive oxygen species to E. coli). Results: Despite scoring poorly on the majority of psychological and caregiving variables, neutrophil function in caregivers was comparable to that in controls and was unexpectedly higher in older adults when compared to younger adults overall. However, those caregivers who reported higher psychological morbidity (depression, perceived stress, poor sleep quality), and more burdensome caregiving showed some evidence of poorer neutrophil phagocytic function. Conclusion: To our knowledge, this is the first study to examine the effect of caregiving stress on neutrophil function in young and older participants simultaneously. Overall, neutrophil function was preserved in caregivers with neutrophil phagocytosis compromised only in those with the highest levels of distress. This suggests that, in future studies, more attention should be paid to individual differences among caregivers rather than caregiving status per se. Statement of contribution: What is already known on this subject? Ageing is accompanied by the decrease in innate and adaptive immunity, termed immunosenescence. Caregiving stress has been shown to exert negative effect on immune function in both young and old. What does this study add? The study examined effect of caregiving and ageing simultaneously in four groups of participants. Neutrophil function and stress hormone levels were preserved in the stressed in both age groups. Those with higher psychological morbidity had poorer neutrophil phagocytosis.