Caregivers have been found to experience high levels of depression and anxiety. This study explored the efficacy of two writing interventions aimed at reducing psychological distress in informal caregivers and examined the moderating effects of alexithymia. Caregivers (N = 150) were randomly assigned to (1) write about the stress related to being a caregiver, (2) write about positive life experiences or (3) write about a control topic for 20 min on 3 days at home. Depression and anxiety symptoms were assessed at baseline, 2 weeks, 2 months and 6 months post-intervention. Analysis of variance for a mixed design revealed no main effects of writing condition on the follow-up measures. However, among caregivers with lower scores on alexithymia, those who wrote about positive experiences reported less anxiety and/or depression on follow-ups at 2 weeks, at 2 months and at 6 months. Moreover, in the control condition, less anxiety was reported by caregivers with lower scores on alexithymia at 2 weeks and at 6 months. No effects of stress disclosure were observed; therefore, writing about caregiver stress should not be encouraged in this vulnerable group. These findings highlight the importance of examining moderating factors, such as individual differences variables as well as exploring the efficacy of alternative writing interventions.