BackgroundCaregivers of people with serious mental illness experience challenges that may affect their mental health. Few researchers have explored whether positive or negative caregiver experiences differ due to disorder characteristics of the person receiving care. We aimed to determine whether caregiver appraisals and psychological functioning differed between caregivers of those diagnosed with schizophrenia spectrum (SSD) and bipolar disorder (BD). MethodsCaregivers of people with SSD and BD participated in an online self-report survey assessing appraisals, distress, anxiety, depression, and psychological wellbeing. Independent samples t-tests and multivariate generalised linear models determined group differences, and Pearson correlation coefficients and Fisher z-score transformations determined differences in the strength of correlations between groups. Results108 caregivers participated in the study. Caregivers of people with SSD reported significantly greater negative appraisals of the care recipient's negative symptoms and dependency. Caregivers did not differ on positive appraisals. Both groups reported moderate distress, mild anxiety and depression, and moderate psychological wellbeing, but did not differ. Higher negative caregiver appraisals were more strongly associated with higher distress, anxiety and depression, and lower psychological wellbeing, for caregivers of those with SSD than BD. LimitationsSmall between group sample sizes, and analyses may have been moderated by significant demographic differences between groups. ConclusionsCaregivers can experience difficulties associated with their role, and some differences may be attributed to the care recipient's disorder. Future research and interventions should consider specific disorder characteristics, such as symptom profiles, to better support caregivers in having their specific needs addressed whilst themselves providing care.