Background: Social support is a key component in maintaining cancer caregiver well-being, and many resources exist to facilitate caregivers' use of social support (eg, cancer support groups). This study sought to determine how informal cancer caregivers use social resources over the course of caregiving.; Methods: The data are from the Comprehensive Health Enhancement Support System study of informal caregivers (n = 202) of patients with recently diagnosed lung cancer. Caregivers self-reported their sociodemographic and caregiving characteristics and social resource use over 6 months. Generalized additive models were used to assess social resource use over time, and generalized estimating equation logistic regression models were used to assess the correlates of social resource use.; Results: Nearly two-thirds of caregivers reported any social resource use. The most prevalent social resources were faith-based groups (38%) and social clubs (30%). Only 1 in 4 caregivers participated in a formal resource such as counseling (11%) or a cancer support group (6%). Social resource use was lowest immediately after the diagnosis and increased over time. Formal resource use exhibited a nonlinear association with time such that formal resource use peaked approximately 9 to 10 months after the cancer diagnosis. Caregivers were more likely to report social resource use if the patient also reported social engagement.; Conclusions: This study has found that many cancer caregivers do not use social resources, although social resource use increases over time after the cancer diagnosis. Because of the association between social engagement and well-being, this information may inform future research and interventions to improve outcomes for cancer caregivers and their families.