Background Electronic mental health literacy (eMHL) is critical for accessing and effectively using digital mental health resources. However, there is a paucity of research on how eMHL varies across age groups. Objective This study aimed to investigate differences in eMHL among young, middle-aged, and older adults; provide insights into the needs, behaviors, and attitudes of different age groups in relation to digital mental health resources; and ultimately, inform the improvement of mental health services. Methods A qualitative investigation was conducted to examine the differences in eMHL across different age demographics in the Chinese population in 2023. The study sample comprised 3 distinct age groups: 18-34 years, 35-64 years, and 65 years and older. Participants were recruited through purposive sampling to ensure a diverse representation of the population. Data were collected through semistructured one-on-one interviews, which allowed for in-depth exploration of individual experiences and perceptions. The gathered data were subsequently subjected to rigorous thematic analysis to enable the identification and interpretation of recurring patterns and themes. Results The principal outcomes derived from these interviews were synthesized into 5 distinct dimensions: emotional needs, use of digital mental health resources, assessment of digital mental health information, engagement with social media to regulate emotions, and coping strategies. These dimensions were uniformly observed across the 3 age groups. Conclusions We identified differences in knowledge, skills, and attitudes regarding the use of web-based information for managing mental health problems between the 3 age groups. The findings highlight the importance of age-specific strategies for improving eMHL.