Empathic accuracy, the ability to accurately understand other people’s emotions, is typically viewed as beneficial for mental health. However, empathic accuracy may be problematic when a close relational partner is depressed because it promotes shared depression. Across two studies, we measured empathic accuracy using laboratory tasks that capture the ability to rate other people’s emotional valence accurately over time: first in a sample of 156 neurotypical married couples (Study 1; total N = 312), and then in a sample of 102 informal caregivers of individuals with dementia (Study 2). Across both studies, the association between empathic accuracy and depressive symptoms varied as a function of a partner’s level of depressive symptoms. Greater empathic accuracy was associated with (a) fewer depressive symptoms when a partner lacked depressive symptoms, but (b) more depressive symptoms when a partner had high levels of depressive symptoms. The ability to accurately detect changes in other people’s emotional valence may underpin shared depressive symptoms in dyads.