INTRODUCTION: Shared decision-making (SDM) is an ideal model for a therapeutic relationship that can improve health outcomes. Healthcare professionals are a critical part of SDM, and they play an important role in the practices of SDM in the clinical setting. Evidence suggests that adolescents diagnosed with depression can benefit substantially from SDM. However, mental health professionals' (MHPs) practices of SDM for adolescents diagnosed with depression in China are not well-documented. This study aimed to investigate the practices of SDM for adolescents diagnosed with depression from the viewpoints of MHPs in China. In this cross-sectional study, we recruited a total of 581 MHPs by convenience sampling. The Shared Decision-Making Questionnaire-Physician Version (SDM-Q-Doc) was used to evaluate the MHPs' practices of SDM for adolescents diagnosed with depression. The mean SDM-Q-Doc was 80.47 (±16.31). Within the six specific decision-making situations, most MHPs selected non-SDM (52.7%-71.6%). Substantial numbers of respondents believed that MHPs made the final decision, especially with regard to the development (37%) and adjustment of medication regimens (42%). The practice of SDM was predicted by MHPs' preference for providing information, their trust in consumers, preference for family involvement in treatment decision-making, working in an outpatient clinic and receiving SDM training (F = 23.582; p = .000; R2 = .198; adjusted R2 = .189). Although the MHPs' self-rated score of SDM-Q-Doc was high, SDM was not extensively applied in the daily management of adolescents diagnosed with depression. Thus, SDM needs to be further promoted by enhancing SDM-related training for MHPs, thereby actively promoting the involvement of families, facilitating the information sharing for consumers and families, and building an active, trusting consumer-practitioner relationship. MHPs should prioritise information sharing with consumers and families, as well as build trusting and friendly therapeutic relationships. Family involvement in treatment decisions should be encouraged when adolescents diagnosed with depression are in need. Actively participating in training related to SDM is also important. Future high-quality evidence is still needed to explore the facilitators and barriers to SDM practices from a tripartite perspective of MHPs, adolescents diagnosed with depression and their families.