The goal of this study is to examine parent and child agreement of child posttraumatic stress disorder (PTSD) symptoms pre- and posttreatment, as well as potential moderators of agreement including treatment responder status, child anxiety control, and parent self-reported PTSD symptoms. We examined child self-reported and parent-reported child PTSD symptoms from the Diagnostic Interview Schedule for Children. Of the 141 parent-child pairs, the mean age of children was 12.72 (SD = 3.40), 53% were female, and 54% were Black. A subsample of participants (n = 47) was assessed after completion of a cognitive behavioral therapy treatment for PTSD. Moderate levels of agreement were found at baseline, though Criterion D (increased arousal) symptoms had lower levels of agreement than the other symptom clusters. Symptom agreement was lower at posttreatment. Treatment responders had higher levels of baseline informant agreement than treatment nonresponders. Child perceived anxiety control significantly moderated informant agreement, such that pairs with children who had high levels of perceived control of their anxiety had lower PTSD symptom agreement where children reported lower symptoms relative to their parents. Contrary to expectations, parent self-reported PTSD did not moderate parent-child symptom agreement. Factors associated with higher parent-child agreement of child PTSD symptoms were being a PTSD treatment responder and children with lower perceived anxiety control. These findings have potential implications for determining those who may benefit from greater symptom monitoring over the course of intervention and potential alternative intervention approaches.