Purpose: Investigate whether Life Review Therapy and Memory Specificity Training (LRT-MST) targeting incurably ill cancer patients may also have a beneficial effect on caregiving burden, symptoms of anxiety and depression, and posttraumatic growth of the informal caregivers. Methods: Data was collected in the context of a randomized controlled trial (RCT) (secondary analyses) on the effect of LRT-MST among incurably cancer patients. Informal caregivers of participating patients were asked to complete outcome measures at baseline (T0), post-intervention (T1), and 1-month follow-up (T2): caregiver burden (caregivers reaction assessment scale (CRA)), symptoms of anxiety and depression (hospital anxiety and depression scale), and posttraumatic growth (posttraumatic growth inventory). Linear mixed models (intention to treat) were used to assess group differences in changes over time. Effect size and independent samples t tests were used to assess group differences at T1 and T2. Results: In total, 64 caregivers participated. At baseline, 56% of the caregivers experienced anxiety and 30% depression. No significant effect was found on these symptoms nor on posttraumatic growth or most aspects of caregiver burden. There was a significant effect of LRT-MST on the course of self-esteem (subscale CRA) (p = 0.013). Effect size was moderate post-intervention (ES = − 0.38, p = 0.23) and at 3-month follow-up (ES = 0.53, p = 0.083). Conclusions: Many caregivers of incurably ill cancer patients experience symptoms of anxiety and depression. LRT-MST does not improve symptoms of depression and anxiety, negative aspects of caregiver burden, or posttraumatic growth. LRT-MST may have a protective effect on self-esteem of informal caregivers (positive aspect of caregiver burden). Trial registration number: Netherlands Trial Register (NTR 2256), registered on 23-3-2010.