Background and aim Healthcare professionals are regularly exposed to moral challenges in patient care potentially compromising quality of care and safety of patients. Preventive clinical ethics support aims to identify and address moral problems in patient care at an early stage of their development. This study investigates the occurrence, risk factors, early indicators, decision parameters, consequences and preventive measures of moral problems. Method Semi-structured expert interviews were conducted with 20 interprofessional healthcare professionals from 2 university hospitals in Basel, Switzerland. A Likert scale questionnaire was completed by the interviewees and analysed using descriptive and inferential statistics. Results Healthcare professionals are frequently exposed to a variety of moral problems, such as end-of-life decisions, resource allocation and assessing the patient's will or decisional capacity. Thirty-four different risk factors for moral problems are identified, e.g. patient vulnerability, divergent values or world views, inadequate resources or poor ethical climate. Twenty-one early indicators are recognised such as disagreement between healthcare professionals, patients and relatives, emotional disturbances, gut feeling or conflict of conscience. A variety of preventive measures are suggested and presented in a preventive clinical ethics support process model. The most helpful measures are early ethical conversations with colleagues, early team-internal ethical case discussions and an ethics-trained contact person on the ward. Ethics training, kerbside consultations, proactive ethics consultations, ethics screening and rounds are also considered helpful. Conclusions Clinical ethics support services should not only offer reactive and complex, but also proactive and low-threshold support for healthcare professionals, patients and relatives.