Purpose: Personality characteristics of the caregiver might play a role in the relation between informal caregiving and health-related quality of life as well as life satisfaction. However, a limited body of research has examined this relation. This study aimed to examine the role personality characteristics of the caregiver might play in the relation between informal caregiving and well-being outcomes using a longitudinal approach.; Methods: Data were derived from the large Panel 'Labour Market and Social Security.' This is an annual household survey, which is conducted by order of the Institute for Employment Research covering persons and households registered as residents of Germany. The SF-12 was used to capture health-related quality of life (covering physical and mental health). A short version of the Big Five Inventory (BFI-K) was used to quantify personality factors. Life satisfaction was measured by a single-item measure. Concentrating on these factors, we used data from the third (2008/2009), sixth (2012), and ninth wave (2015). 34,548 observations were used in fixed effects regressions.; Results: Adjusting for various potential confounders, linear fixed effects regressions showed that the onset of informal caregiving reduced life satisfaction (β = - .14, p < .01), but not physical and mental health. The relation between informal caregiving and life satisfaction was significantly moderated by agreeableness (p < .01).; Conclusions: Findings of the present study emphasized that agreeableness moderates the relationship between informal caregiving and life satisfaction. Measuring personality characteristics of the informal caregiver is important for tailoring interventional strategies in order to increase the benefit of these programs.