To protect research participants and ensure scientific integrity in clinical trials, independent data monitoring committees (DMCs, also known as data and safety monitoring boards) increasingly oversee randomized clinical trials and recommend modifying or stopping research. Little is known about the ethical issues DMCs face. We conducted semistructured interviews of DMC members using a qualitative description approach with low‐inference interpretation. We recruited respondents through consultation with experts, an online registry of DMC members, and snowball sampling. We interviewed 22 DMC members who were statisticians, clinicians, and/or ethicists that had overseen a wide variety of trials globally. We identified three themes: finding common ground on responsibilities with variation; the need for judgment but not necessarily ethics expertise; and the resulting emotional distress from navigating ethical challenges. In the first case, DMC members identified 19 distinct duties, with some ethical responsibilities rarely mentioned. In the second case, not all DMC members saw the need for ethicists on DMCs or ethics training. In the third case, ethical challenges sometimes led to strong negative emotions. Developing tailored ethics training and decision‐making procedures may help DMCs respond more effectively to ethical challenges.