To evaluate and estimate the effect of psychosocial interventions on improving the quality of life (QoL) of adult cancer caregivers. We conducted a systematic review of randomized controlled trials among adult cancer caregivers published from 1947 to 2011. Rigorous inclusion criteria included randomization of caregivers, use of control groups, and at least one active psychosocial intervention where caregiver QoL was measured. A pair of raters independently reviewed all abstracts, and studies were assessed for quality using an 11-item PEDro coding scale. Data were extracted, examined, and synthesized using a narrative approach. Six randomized controlled trials met inclusion criteria out of 1066 identified abstracts. Studies were rejected because of methodological flaws and failure to report a measure of caregiver QoL. A total of 1115 caregivers were included at baseline measurements. Estimated effect sizes for included studies were nil to small ranging from 0.048 to 0.271. Studies with larger effect sizes targeted caregivers' problem-solving and communication skills. Interventions targeting problem-solving and communication skills may ease the burdens related to patient care and role changes associated with care while improving caregiver's overall QoL. Further research is needed to establish efficacy of interventions across all stages of the 2cancer caregiving experience, especially focusing on issues of caregiver retention, caregiver relationships to the cancer patient, and individual differences in caregiver experiences with different types of cancer. Copyright © 2012 John Wiley & Sons, Ltd.