A substantial number of patients do not improve from psychotherapy, some even deteriorate, and some terminate treatment prematurely. Identifying therapist variables that may lead to treatment failures from patients' perspectives can inform how psychotherapists can increase effectiveness. Using a semistructured protocol, we interviewed 24 patients who had experienced unsatisfying individual face-to-face psychotherapy within the last 2 years. The study procedures were guided by the consolidated criteria for reporting qualitative research. The manifest content analysis provided 13 subcategories grouped into four categories: (a) psychotherapists' negative traits (inflexible, unengaged, unemphatic, insecure), (b) unprofessionalism (superficial, violating personal boundaries, breaking confidentiality, nontransparent), (c) incompetence (unstructured, poor assessment or understanding, poor knowledge, too passive), and (d) mismatch (therapist-patient mismatch). To reduce the risk of treatment failure, psychotherapists may need a multifaceted set of relational skills, theoretical and technical competence, ethical sensitivity, and engagement. Some of the identified subcategories were complex constructs (e.g., unengaged) that may need time and effort to develop for psychotherapists. Other identified subcategories were obvious inappropriate behaviors in professional psychotherapy (e.g., breaking confidentiality). However, the categories found in this study need further quantitative investigation to assess the validity, frequency, and relative impact on treatment outcomes. Clinical Impact Statement Question: What psychotherapist shortcomings do patients perceive are associated with treatment failure? Findings: Patients' perception could be grouped into four main categories: negative traits, unprofessionalism, incompetence, and mismatch. Meaning: Psychotherapists and clinical supervisors may need to be aware of the therapist shortcomings identified in this study to increase the quality of their clinical work and reduce the risk of patient dropout. For example, psychotherapists may need to ensure that they convey warmth and empathy while supervisors may need to monitor potential violations of therapist-patient confidentiality. Next Steps: These qualitative results need to be replicated and validated by large-scale quantitative data collection to assess the prevalence of the different therapist shortcomings. Means to counter therapist shortcomings need to be developed and implemented in quality assurance systems.