Objectives: Research on unretirement (retirees who re-enter the workforce) is burgeoning. However, no longitudinal study has examined how informal care relates to unretirement. Utilizing role theory, this study aims to explore the heterogeneity of informal care responsibilities in retirement and to examine how informal care informs re-entering the workforce in later life.; Method: Data were drawn from the Health and Retirement Study of fully retired individuals aged 62 years and older in 1998 (n = 8,334) and followed to 2008. Informal care responsibilities included helping a spouse/partner with activities of daily living (ADLs) or instrumental activities of daily living (IADLs); helping parent(s) or parent-in-law(s) with ADLs or IADLs; and single or co-occurrence of care roles. Covariates included economic and social factors. Cox proportional hazard models were utilized.; Results: When compared with noncaregivers, helping a spouse with ADLs or IADLs reduced the odds of returning-to-work in the subsequent wave by 78% and 55%, respectively (hazard ratio [HR]: 0.22, confidence interval [CI]: 0.06-0.87; HR: 0.45, CI: 0.21-0.97). There was no statistical difference to returning-to-work between noncaregivers and helping parents with ADLs/IADLs or multiple caregiving responsibilities.; Discussion: Role theory provided a useful framework to understand the relationships of informal care and unretirement. Aspects of role strain emerged, where, spousal caregivers were less likely to come out of retirement. Spousal caregivers may face challenges to working longer, and subsequently, opportunities to bolster their retirement security are diminished. Research and policy implications are discussed.