Purpose <p>It has been documented that childhood maltreatment is associated with many psychological problems as a transdiagnostic risk factor. However, few studies have investigated the relationship between childhood maltreatment and both internalizing and externalizing symptoms, along with the underlying mechanisms. The current study aimed to investigate the role of emotion dysregulation in the relationship between childhood maltreatment and internalizing and externalizing symptoms.</p> Methods <p>The sample included 301 participants aged 18 and above (<i>M</i>_<i>age</i> = 23.78, <i>SD</i> = 6.08). Participants completed questionnaires regarding childhood maltreatment, emotion dysregulation, depression, anxiety, post-traumatic stress symptoms, and aggression using an online platform. Structural equation modelling was used to explore the relationships among the variables.</p> Results <p>The results showed that (a) childhood maltreatment was positively associated with both internalizing <i>(β</i> = 0.69, <i>p</i> &lt;.01) and externalizing symptoms (<i>β</i> = 0.51, <i>p</i> &lt;.01); (b) the emotion dysregulation mediated the relationship between childhood maltreatment and both internalizing (effect size = 0.29, <i>SE</i> = 0.04, <i>p</i> &lt;.001, 95<i>%</i> CI [0.21, 0.38]) and externalizing symptoms (effect size = 0.21, <i>SE</i> = 0.04, <i>p</i> &lt;.001, 95<i>%</i> CI [0.13, 0.29]).</p> Conclusions <p>Our results revealed that childhood maltreatment and emotion dysregulation could be crucial transdiagnostic risk factors for both internalizing and externalizing symptoms. These findings suggest the importance of supporting emotional regulation among individuals with a history of childhood maltreatment.</p>