Seizure disorders affect not only the individual living with seizures, but also those caring for them. Carer–patient relationships may be influenced by, and have an influence on, some aspects of living with seizure disorders — with potentially different interactions seen in epilepsy and psychogenic nonepileptic seizures (PNES). We studied the influence of patient and carer attachment style and relationship quality on carer wellbeing and psychological distress, and explored whether these associations differ between carers for people with epilepsy and for those with PNES. Consecutive adult patients with epilepsy (N = 66) and PNES (N = 16) and their primary informal carers completed questionnaires about relationship quality, attachment style, and psychopathological symptom burden. We used correlation analysis to identify associations between relationship quality, attachment style, and carer depression, anxiety, and wellbeing; and to explore differences in these associations between carers for people with epilepsy and for those with PNES. Overall, 25.3% of carers for people with epilepsy or PNES had scores above the clinical cutoff for depression and 39.6% for anxiety; significantly more carers for people with PNES reported clinically significant depression (47.1% vs. 20.0%), but there was no difference in anxiety rates likely to be of clinical relevance. Correlations differed significantly between carers for people with epilepsy and for those with PNES in terms of patient quality of life and carer anxiety (r E = − 0.577, r PNES = − 0.025); seizure severity and carer depression (r E = 0.248, r PNES = − 0.333) and mental wellbeing (r E = − 0.356, r PNES = 0.264); patient depression and carer anxiety (r E = 0.387, r PNES = − 0.266); and patient anxious attachment and carer anxiety (r E = 0.382, r PNES = 0.155). Clinically evident levels of psychological distress are prevalent among carers for people with epilepsy and PNES. Clinical and relationship variables affect carer quality of life differently depending on whether care is provided for individuals with epilepsy or PNES. • Carers for people with seizure disorders experience high levels of depression and anxiety. • Mental wellbeing in this group correlates with relationship conflict, and patient and carer attachment styles. • These associations differ between carers for people with epilepsy and for those with psychogenic non-epileptic seizures.