Background Volunteers working in earthquake-stricken areas have personally experienced or witnessed many traumatic events.The aim of this study is to investigate the levels of post-traumatic stress disorder (PTSD), anxiety, and depression in individuals who volunteered during a highly destructive earthquake. Methods A descriptive research design was conducted between 20.03.2023 and 20.06.2023, with the study population consisting of volunteers who went to the earthquake-stricken area. An online survey was used as the data collection tool and was distributed to volunteers involved in earthquake-related activities through non-probability sampling via communication groups. The survey included sociodemographic questions, the Generalized Anxiety Disorder 7-item scale (GAD-7), the CES-Depression Scale, and the Post-Traumatic Stress Disorder (PTSD) Checklist. Results A total of 237 volunteers responded to the survey. The frequencies of anxiety, depression, and PTSD among participants were 23.6% (n = 56), 58.6% (n = 139), and 13.9% (n = 33), respectively. Multivariable logistic regression showed that participants without earthquake-related training had lower odds of anxiety (aOR = 0.35, 95% CI: 0.16–0.76) and depression (aOR = 0.52, 95% CI: 0.29–0.95). Female sex was associated with higher odds of depression (aOR = 3.87, 95% CI: 2.00–7.50) and PTSD (aOR = 2.71, 95% CI: 1.26–5.82), while non-healthcare workers had higher odds of depression (aOR = 1.85, 95% CI: 1.01–3.37). Conclusion Volunteers working in earthquake-stricken areas are at a high risk of depression, anxiety, and PTSD. Therefore, providing appropriate psychosocial support to volunteers involved in disaster response is essential for protecting and maintaining their mental well-being.