Mental health among older adults directly affects their well-being, quality of life, and sociability. The advancement of Internet brings new opportunities and challenges to the mental health of older adults. This study aims to analyze the impact and the mechanisms of internet usage on depression among older adults by analyzing the data from the China Health and Retirement Longitudinal Survey (CHARLS). This study investigated the differences in the impact of Internet usage on older adults’ depression based on Hukou (household registration) and gender. The results indicated that the reduction effect of internet usage on the depression of urban older adults was stronger. The reduction effect of Internet usage on depression of female older adults was stronger. Additionally, family networks and social networks played a mediating role in the relationship between Internet usage and depression. This study also compared the impact of Internet usage on older adults’ depression in different years. The findings suggest that it is essential to make the Internet more accessible for older adults to improve their mental health.