© 2017 Japan Pediatric SocietyBackground: The aim of this study was to investigate the rate of post-traumatic stress disorder (PTSD) and associated risk factors among mothers of children who underwent cancer surgery. Method: This cross-sectional, multi-center study included a total of 60 mothers whose children underwent major thoraco-abdominal surgery and were under follow up in the outpatient setting between February 2016 and May 2016. Clinical Data Form, Hospital Anxiety and Depression Scale (HADS), and Clinician-Administered PTSD scale were used. Results: Of all participants, 13 (21.7%) were diagnosed with PTSD. These mothers had shorter duration of marriage, longer duration of hospital stay after surgery, and higher HADS scores, compared with the others without PTSD. Thoughts of guilt such as “I am being punished or tested” were more frequent in mothers with PTSD. Insomnia, irritability, concentration problems, and psychological reactivity were the most common symptoms. Conclusion: Post-traumatic stress disorder is a severe disorder that may worsen the daily functioning of mothers and may also have an unfavorable effect on child. It is therefore of utmost importance for clinicians to recognize PTSD and the associated risk factors in order to guide these parents.