BACKGROUND: Diet and exercise interventions for cancer survivors result in health benefits; however, few studies have examined health outcomes in relation to adherence. PURPOSE: We examined associations between adherence to components of a diet-exercise intervention and survivors' physical and mental health. METHODS: A randomized controlled trial tested a telephone and mailed print intervention among 641 older, overweight, long-term survivors of breast, prostate, and colorectal cancer. Dietary and exercise behaviors were assessed at 14 time points throughout the year-long intervention; health outcomes were examined postintervention. RESULTS: Telephone session attendance had significant indirect relationships with health outcomes through intervention-period exercise and dietary behavior. Attendance showed positive indirect relationships with physical function (β = 0.11, p < 0.05), basic and advanced lower extremity function (β = 0.10, p < 0.05/β = 0.09, p < 0.05), and mental health (β = 0.05, p < 0.05), and a negative indirect relationship with body mass index (β = -0.06, p < 0.05). CONCLUSIONS: Session attendance is vital in facilitating improvement in health behaviors and attendant outcomes (Clinicaltrials.gov number NCT00303875).