Aim To investigate the association between spouse cognitive status and depressive symptoms in cohabiting spouses, and to further analyze how participation in social network‐enhancing activities interplays in the objected relationship. Methods Data from the Korean Longitudinal Study of Aging, 2006–2012, were used. A total of 2782 male and 2515 female married participants currently cohabiting with their partners were included in the baseline. The association between spouse cognitive status and depressive symptoms, measured using the Center for Epidemiological Studies Depression scale, was investigated through the generalized estimating equation model. Results When setting the participants living with spouses of normal cognitive function as reference, participants living with spouses having mild dementia (male β 0.7349, P ≤ 0.0001; female β 0.8042, P ≤ 0.0001), and moderate and severe dementia (male β 1.1504, P ≤ 0.0001; female β 1.2462, P ≤ 0.0006) showed higher depression scores in a dose–response relationship. Additionally, male and female subjects participating in social network facilitating activities had lower increases in depression scores than their non‐participating counterparts. Conclusions Spouse cognitive impairment is associated with increasing depression scores in cohabiting caregivers. Individuals not participating in social network‐facilitating activities are more vulnerable to the negative mental health effects of spouse cognitive impairment. Hence, considering the increasing importance of late life depression and cognitive decline in aging societies, it is important to note the protective effects of social network and support in addressing the mental health of spouse caregivers. Geriatr Gerontol Int 2017; 17: 973–983.