Background: Worldwide, the high number of mental disorders poses challenges for healthcare systems. In 2020, digital health applications (DHA) were introduced in Germany as a novel type of healthcare financed by the statutory health insurance, aiming to detect, monitor, treat, or alleviate disease, injury, or disability. DHA for mental disorders (DHA-MD) intend to support outpatient care. However, there is limited evidence on general practitioners (GPs) perspectives on the use and benefits of DHA-MD in primary care. Methods: A mixed-methods study was conducted between January and October 2024, including a nationwide online survey and qualitative interviews with GPs from Germany. Sampling was conducted in collaboration with German practice-based research networks. The questionnaire and interview guide were developed by the study team using the domains of the Consolidated Framework for Implementation Research. Descriptive analyses of (un)suitable patient groups and treatment contexts for the use of DHA-MD in primary care were conducted. The interviews with GPs were analyzed using qualitative content analysis. Results: A total of 149 GPs participated in the survey and 12 GPs were interviewed. Most GPs reported that they would prescribe DHA-MD primarily to patients with prior positive experiences with DHA-MD (84.2%), aged 18-35 years (79.6%), with limited geographical mobility (78.6%), and when there is a need to bridge waiting times for psychotherapy (83.3%). In contrast, they would not prescribe DHA-MD to patients over 80 years (95.2%), under 18 years (87.0%), with multiple mental disorders (80.7%), and as primary treatment method (81.1%). In the interviews, GPs primarily viewed younger to middle-aged patients, with the necessary digital affinity and motivation to use the DHA, as well as with mild to moderate mental disorders as suitable. They reported to prescribe DHA-MD especially in waiting times and to support in-person care. Conclusions: GPs take into account patients’ individual skills, clinical condition, motivation, and likelihood of engaging with the DHA-MD when prescribing it. However, to avoid the systematic exclusion of certain patient groups, shared decision-making should be used to assess whether individual patients would benefit from using a DHA-MD. This assessment should be based on individual capabilities, such as digital literacy.