This study aimed to compare longitudinal change of the psychological distress of a group with psychological first aid (PFA) experience and a group without PFA experience among physicians and other healthcare professionals from before the novel coronavirus disease (COVID-19) pandemic to during the pandemic. The baseline survey was conducted in January 2020 (T1). The respondents in T1 were invited to participate in March (T2) and November 2020 (T3). Psychological distress was assessed by the Kessler 6 Scale. Participants were divided into two categories: a group with and a group without PFA experience. Participants were further divided between physicians and healthcare professionals other than physicians, because physicians are more likely to experience morally injurious events. A mixed-model repeated-measures ANOVA was conducted as an indicator of the group differences. In T1, 398 healthcare professionals participated. The longitudinal analysis of healthcare professionals other than physicians showed that psychological distress was significantly greater in the group without PFA experience than in the group with PFA experience (T1 vs. T3). This study showed psychological distress among healthcare professionals other than physicians was significantly greater in the group without PFA experience than in the group with PFA experience during the COVID-19 pandemic, but the results were not consistent among physicians.