Exposure to adverse events during childhood and adolescence is associated with problematic outcomes across the life span, including the development of posttraumatic stress disorder (PTSD). A growing body of research examining the effectiveness of eye movement desensitization and reprocessing (EMDR) therapy in treating PTSD among young people has yielded mixed findings. More work is needed that elucidates whether EMDR is linked to positive and sustained reductions in symptoms among youth who experience potentially traumatic events. For this open trial, we analyzed data from 143 youth (Mage = 12.9, standard deviation [SD] = 3.4, Range = 6–18) who received outpatient behavioral health clinic services, including EMDR. We assessed whether the number of types of exposure to family-related and non-family-related traumatic events, as well as differences in severity of PTSD symptomatology, was associated with changes in internalizing and externalizing problem behaviors from intake to 6 months. Results indicated that youth with (a) fewer exposures to non-family-related potentially traumatic events and (b) more severe PTSD symptoms, showed greater improvements in externalizing problem behaviors. We discuss limitations of the present study and implications for future research.