Research has evidenced that purpose in life helps to minimise the strains of providing informal care to a significant other, but little is known about whether this psychological resource influences the paths from stressors to the health outcomes of family caregiving and through which mechanisms it can exert this protective effect. This study aimed to explore the moderating role of purpose in life on the (mediated through adaptive coping) relationship between caregiver burden and psychological distress in haemodialysis caregivers. A cross‐sectional study was conducted with a convenience sample of family caregivers (n = 173; M = 55.9, SD = 15.6 years old) of adults undergoing haemodialysis. A moderated‐mediation model was computed to explore the interaction effects of purpose in life on the path between burden and distress, having adaptive coping behaviours as parallel mediators. Results showed that purpose in life had a buffering effect on the mediated (through acceptance coping) relationship between burden and distress (index of partial moderated‐mediation: bsimple = −0.029, 95% bootstrap confidence interval (CI) [‐0.070, −0.002]), and that this conditional effect was lowest at high levels of the moderator (at +1SD: bsimple = 0.038, SE = 0.026, 95% bootstrap CI [0.001, 0.098]). Use of emotional support (F(1,159) = 4.395, p = 0.038) and positive reframing (F(1,159) = 5.648, p = 0.019) also mediated this path. This study expands knowledge about the modifiable internal resources through which purpose in life can help promote psychosocial adjustment to the haemodialysis caregiving process. Mental health promotion initiatives aimed at this population need to consider combining different intervention approaches to foster purpose in life and train adaptive (and flexible) coping skills.