Guided by a life course perspective, this study investigated whether the psychological consequences of transitioning into a caregiver role for a biological parent, parent-in-law, spouse, other kin, or nonkin among married adults might be moderated by marital role quality. Using longitudinal data from a national sample of 1,842 married adults aged 35 years and older, this study estimated regression models examining whether marital disagreement prior to the transition to caregiving predicted differences in change in global happiness and depressive symptoms because of a transition into caregiving. Results indicated that, compared to noncaregivers, new caregivers for a biological parent or spouse experienced both a greater decline in happiness and a greater increase in depressive symptoms when they reported a higher level of marital disagreement. These findings suggest that the psychological effects of becoming a caregiver for a biological parent or spouse among married adults are contingent on marital role quality. (Contains 3 tables and 4 figures.)