Firefighters, whether volunteer or professional, play a crucial role in protecting people, property, and animals, and their interventions often involve providing first aid at the scene of an incident. While additional training for medical first responders (paramedic) is not mandatory, it equips firefighters with essential first aid knowledge through both theoretical and practical components. These skills are particularly important because firefighters are often the first to arrive at the scene of an accident, where rapid and accurate first aid can significantly improve outcomes for the injured. The aim of this study was to assess the level of first aid knowledge among firefighters in the Krapina - Zagorje Country, with a particular focus on the paramedic specialization. Additionally, the study aimed to determine how the elapsed time since the completion of training affects the retention of first aid knowledge, and to identify factors that contribute to the maintenance or decline of these skills. The research was conducted using a quantitative analysis of data collected through surveys and knowledge tests. The study participants included firefighters with varying levels of first aid training, including those specialized as paramedics. The study results revealed a significant negative correlation between the time elapsed since training completion and the level of first aid knowledge. This indicates a gradual decline in knowledge over time. The findings also underscored the importance of continuous education and periodic training to ensure firefighters remain prepared to provide first aid effectively. The study's conclusions highlight the necessity of regular first aid course renewals to maintain a high level of knowledge and readiness among firefighters. Recommendations were made to enhance educational programs and to implement regular refresher courses.