Psychological first aid (PFA) is a world-wide implemented approach to helping people affected by an emergency, disaster, or other adverse event. Controlled evaluations of PFA’s training effects are lacking. We evaluated the effectiveness of a one-day PFA training on the acquisition and retention of knowledge of appropriate responses and skills in the acute aftermath of adversity in Peripheral Health Units (PHUs) in post-Ebola Sierra Leone. Secondary outcomes were professional quality of life, confidence in supporting a distressed person, and professional attitude.