Background Older adult carers of people who experience psychosis are at increased risk of developing physical and mental health problems due to the compounding factors of supporting their care-recipient and the health changes associated with ageing. Effective interventions exist but can be difficult to access and maintain prolonged engagement. Self-directed writing therapies, frequently referred to as Written Emotional Disclosure (WED), might be a suitable alternative intervention to improve the wellbeing of carers. Methods This study aimed to determine the feasibility (recruitment, retention and primary outcome completion) and acceptability of a specific WED intervention known as Positive Written Disclosure (PWD). Informal carers of people with psychosis were randomised to PWD, neutral writing or no writing. Quantitative outcomes including positive and negative affect, carer wellbeing, quality of life, depression, anxiety, stress, self-efficacy, leisure time satisfaction as well as health care utilisation were collected at baseline, 1-, 3-, and 6-month assessments. Qualitative feedback was also collected via questionnaire and semi-structured interviews from those randomised to either writing group. Results We successfully met our progression criteria, recruiting to target and within timeframes whilst attaining 97% retention and 84% primary outcome data completed at 6 months. Carers randomised to the positive writing group described the intervention as enabling them to have a more positive attitude and focus on activities for themselves. Both writing groups described their tasks as providing distraction from caring responsibilities. However, some carers found the narrow positive emotion focus challenging. Conclusions PWD is a feasible and acceptable intervention for older adult carers of people with psychosis within a community setting. Further refinement of the writing protocol to include choice in type of emotion disclosed in addition to screening for some level of need may be required in future trials to reduce floor/ceiling effects of outcomes which may explain the lack of change observed.