This chapter explores ethical principles, dilemmas, and responsibilities involved in conducting mental health and psychosocial support (MHPSS) interventions and research in humanitarian settings. Although interventions and research may require some different considerations, we argue that many of the guidelines and challenges are similar, and the researchers and practitioners can learn from each other. Humanitarian contexts are characterized by conflict, displacement, poverty, and fragile infrastructures, which magnify both human vulnerability and power imbalances between aid providers and affected populations. We review core ethical principles—including respect, beneficence, non-maleficence, and justice—while examining challenges around informed consent, safeguarding, cultural sensitivity, staff well-being, and project closure. Through case studies and critical reflections, the chapter demonstrates that ethical practice in humanitarian MHPSS is strengthened through established principles and guidelines, but is also an ongoing, situated, and reflexive process that demands accountability, humility, and cultural awareness. Although legal structures and formal ethical regulations are necessary and useful, these are not sufficient. We argue that the development of ethical frameworks must be rooted in dialogue with local communities, adapted to context, and responsive to evolving challenges. By recognizing ethical dilemmas as integral to humanitarian work rather than as obstacles to be avoided, researchers and practitioners can strengthen trust, improve practice, and ensure that interventions promote dignity, justice, and sustainable impact.