Introduction. Emergency medical services (EMS) personnel are exposed to stress. Job stress in EMS personnel can reduce their resilience and have adverse effects on their clinical performance and mental health, thus reducing the quality of their work. The present research was performed to determine the effect of psychological hotwash on resilience of emergency medical services personnel. Methods. This study was a quasiexperimental. Sixty-four EMS personnel were randomly divided into two groups of hotwash and control. The psychological hotwash program was performed in the intervention group for a month based on the protocol; however, the control group continued their usual work and received no intervention. A day and six weeks after the psychological hotwash in the intervention group, the resilience of the EMS personnel was remeasured in both groups. Results. Before the intervention, the participants’ mean resilience score was 138.37 ± 7.04 in the intervention group and 137.34 ± 8.48 in the control group. There was a statistically significant difference between the mean scores of resilience in the intervention and control groups a day after the intervention (
P
=
0.003
). There was no statistically significant difference between the mean scores of resilience in the intervention and control groups 6 weeks after the intervention (
P
=
0.102
). Conclusion. The EMS personnel’s attendance at psychological hotwash sessions could increase their resilience. Nevertheless, the sessions should not be interrupted because the 6-week interruption of the sessions caused the nonsignificant scores of resilience in the hotwash and control groups. Hence, it is recommended to continue the investigation of the effects of hotwash on resilience, stress reduction, and job burnout reduction in EMS personnel by other researchers in different settings.