Objectives Caregiving can negatively impact well‐being. Cancer caregivers face unique challenges given the intense nature of cancer and treatment, which increases their risk for burden, poor quality of life (QOL), and burnout. Studies to reduce caregiver burden demonstrate QOL improvement and distress reduction in the short term. However, few studies exist to address long‐term benefits. We assessed changes in various QOL domains after participation in a QOL intervention for caregivers of patients having newly diagnosed advanced cancer. Methods Our institutional review board‐approved study randomized patient–caregiver dyads to either usual care or an in‐person group intervention composed of six 90‐min sessions of structured multidisciplinary QOL components delivered over 4 weeks, with 10 follow‐up phone calls within 20 weeks. Caregivers attended four of the six sessions attended by patients. Sessions included physical therapy, coping and communication strategies, mental health education, spirituality, and social needs. Caregiver QOL (Caregiver Quality of Life Index‐Cancer Scale [CQOLC] and Linear Analogue Self‐Assessment [LASA]) and mood (Profile of Mood States‐Brief [POMS‐B]) were measured at baseline and 4, 27, and 52 weeks. Wilcoxon tests and effect sizes were used to compare the caregiver groups. Results Of the 131 caregivers (65 intervention and 66 usual care), 116 completed the study. Caregivers post‐intervention (at 4 weeks) had improved scores on LASA Spiritual Well‐being; POMS‐B total score, Vigor/Activity, and Fatigue/Inertia; and CQOLC Adaptation. At long term (at 27 weeks), caregivers retained improvement in POMS‐B Fatigue/Inertia and gained improvements in CQOLC Disruptiveness and Financial Concerns. Conclusions Caregivers who received the intervention had higher QOL ratings for specific QOL domains but not for overall QOL. Although a comprehensive intervention was helpful, more specific, targeted interventions tailored for individual needs are recommended. Copyright © 2015 John Wiley & Sons, Ltd.