Ambulance nurses are an important part of the acute care trajectory. Since 2005, Swedish regulations require that every ambulance is staffed by at least one registered nurse. Although specialist training is not mandatory but it is considered beneficial due to the increasing complexity of prehospital care. To support competence development, Swedish prehospital care utilizes concept-based courses such as AMLS, PHTLS, TNCC, and PS. These courses aim to enhance nurses’ ability to manage complex situations. The overall aim of this thesis is to explore ambulance nurses’ self-assessed professional competence, and to assess the impact of participation in concept-based courses on their self-assessed professional competence. Several factors influence ambulance nurses' competence, including education level, work experience, and personal attributes. Specialist nurses often report higher competence in specific areas. Participation in concept-based courses was linked to significantly higher self-assessed competence, particularly in Medical-Technical Care, Supervision, and Leadership. PHTLS and AMLS demonstrated the broadest impact, while PS contributed primarily to improvements in Supervision and Professional Conduct. Further research is needed to understand how various educational interventions such as formal education, specialist training, ongoing development and how it can optimize competence growth. The goal is to establish evidence-based strategies that enhance professional development and improve patient safety. This thesis provides knowledge that can support evidence-based improvements in prehospital care, by highlighting ambulance nurses’ self-assessed competence and the perceived impact of concept-based courses.