This study was conducted to determine the effect of childhood adverse experiences on the risk of postpartum posttraumatic stress disorder (PP-PTSD) and postpartum depression (PPD). This descriptive study was conducted with 417 mothers between 1 March and 30 April 2022. Data were collected using a demographic and obstetric information form, the Adverse Childhood Experiences Questionnaire (ACE), City Birth Trauma Scale (CityBiTS) and Edinburgh Postpartum Depression Scale (EPDS) through the Google Forms platform. The mothers participating in the study had a mean age of 30.47 ± 4.21 years, 65.9% (n = 275) had at least one ACE, 10.3% (n = 43) met all of the DSM-5 PTSD criteria according to the CityBiTS, and 91.8% (n = 383) had at least one traumatic stress symptom. Correlation analysis revealed weak positive associations between number of ACEs and CityBiTS score (p < 0.001, r = 0.328) and EPDS score (p < 0.001, r = 0.291) and a moderate positive association between CityBiTS and EPDS scores (p < 0.001, r = 0.601). PP-PTSD was found to be a partial mediator variable between ACE and PPD. The presence of ACE in mothers was found to increase the risk of developing PPD, both alone and when combined with traumatic birth experience. Therefore, we believe that screening for a history of ACE during pregnancy, investigating traumatic birth experiences in the postpartum period, closer follow-up of mothers with both ACE and traumatic birth experiences and increasing support systems will be beneficial in the prevention and early diagnosis of PPD.