Background: In Germany, not only physicians are allowed to practice medicine but also non-medically trained practitioners, so-called Heilpraktiker, can obtain a licensure to treat patients. In contrast to cooperation between doctors, a division of tasks and responsibilities between non-medically trained practitioners and physicians seems to be difficult. The aim of the study was to clarify to what extent doctors in private practice are willing to cooperate with non-medically trained practitioners. At the same time, conditions, opportunities, and obstacles of cooperation are described. Methods: In order to evaluate the willingness to collaborate with non-medically trained practitioners, semi-structured interviews were conducted with 15 physicians and 2 dentists in an outpatient setting. The interviews further focused on conditions, advantages, and obstacles to cooperation. The interviews were transcribed literally and analyzed using qualitative content analysis. Results: The interviews showed that physicians partly are willing to cooperate with non-medically trained practitioners, but there were strict conditions and also some serious obstacles to cooperation. Doctors who are open-minded about collaboration consider non-medically trained practitioners as additional therapists for minor ailments. Non-medically trained practitioners would have to respect their limitations, and health insurances should launch transparent contracts for remuneration and reimbursement. Physicians showed low confidence in training programs for Heilpraktiker. Additionally, it was thought to be harmful when non-medically trained practitioners interfere with the physician-patient relationship and try to interrupt conventional treatment or medication. Conclusions: Quantitative research is necessary to quantify data and generalize results from the sample to the population of physicians. Further, the willingness of non-medically trained practitioners to collaborate with physicians should be evaluated. Physicians should try to reduce communication obstacles so that patients can speak frankly about consultations of non-medically trained practitioners.