Late-life depression has become a growing concern worldwide. Diagnostic uncertainty pervades in online medical consultations, where family members of older adults with suspected depression seek confirmation of the diagnosis. However, how doctors communicate diagnostic uncertainty to family members has not been studied in these online medical consultations. The study thus aimed to unpack doctors’ discursive strategies of communicating diagnostic uncertainty to family members of older adults with suspected depression during online medical consultations. Data were collected from a health consultation website and analyzed using mediated discourse analysis. The findings demonstrated that doctors adopted four implicit strategies to communicate diagnostic uncertainty to family members, including using tentative language, providing diagnostic possibilities, offering candidate diagnoses contingent upon specific conditions, and attributing patients’ symptoms to potential mental health issues without assigning a definitive diagnostic label. These discursive strategies could be incorporated in training programs for doctors to improve their skills of communicating diagnostic uncertainty to patients and family members.