Worldwide, an increasing number of transgender individuals turn to gender identity clinics for gender-affirming medical care: interventions to affirm and express their experiences gender. A central ethical challenge faced by those receiving and providing such care is: How should we go about making and sharing decisions? In other words: what does good shared decision-making entail? This thesis has two central aims. First, to gain insight into the moral and conceptual landscape of shared decision-making in this specific care practice. Second, to co-create an ethics support tool that fosters (a joint reflection on) good shared decision-making making and aids stakeholders in practice in recognizing and handling related ethical challenges. Amid polarization, we sought to bring together and encourage deliberation among healthcare professionals and clients through a participatory design, qualitative methods, and ethics. This thesis highlights that shared decision-making in gender-affirming medical care is characterized by ontological ambiguities, epistemic uncertainties and normative contestations. We hope the findings and tool presented in this thesis provide a foothold for ongoing, critical-constructive dialogues toward better shared decision-making in transgender healthcare and beyond.