Background Older patients are often vulnerable and highly dependent on healthcare professionals’ assessment in the event of acute illness. In the context of ambulance services, this poses challenges as the assessment is normally conducted with a focus on identifying life-threatening conditions. Such assessment is not fully satisfactory in a patient relationship that also aims to promote and protect patient autonomy. Aim To describe ambulance clinicians’ understanding of older patients’ self-determination when the patient’s decision-making ability is impaired. Research design A qualitative (...) design with an inductive approach, guided by descriptive phenomenology. Participants In total, 30 ambulance clinicians, comprised of 25 prehospital emergency nurses, 1 nurse and 4 emergency medical technicians participated in 15 dyadic interviews. Ethical considerations The research was conducted in accordance with the Declaration of Helsinki, and permission was granted by the Swedish Ethical Review Authority. Findings The findings are presented in two themes: (1) Movement between explicit and implicit will; and (2) Contradictions about the patient’s best interests. The clinicians’ interpretations are based on an understanding of the patient’s situation using substitute decision-making in emergency situations and conversations that reveal the patient’s explicit wishes. Sometimes the clinicians collaborate to validate the patient’s implicit will, while they at other times subordinate themselves to others’ opinions. The clinicians find themselves in conflict between personal values and organisational values as they try to protect the patient’s self-determination. Conclusion The results indicate that older patients with an impaired decision-making ability risk losing the right to self-determination in the context of ambulance services. The clinicians face challenges that significantly affect their ability to handle the older patient’s unique needs based on a holistic perspective and their ability to be autonomous. (shrink)