Witnessed violence has significant negative consequences for youth behavior and mental health. However, many findings on the impact of witnessed violence have been based on a single informant. There is a general lack of consistency between caregiver and youth reports on both witnessed violence and behavioral problems. This study included data from both caregivers and youth and incorporated a multisource analytic approach to simultaneously examine the association between youth witnessed violence and externalizing and internalizing behavior problems. Data from 875 caregivers and 812 youth were collected as part of the Longitudinal Studies of Child Abuse and Neglect (LONGSCAN). Findings showed that youth reported more witnessed violence than did their caregivers, and caregivers reported more externalizing and internalizing behavior problems than did youth. Further, the source of information had a significant impact on the association between witnessed violence and internalizing behaviors. These findings highlight the need to incorporate multiple sources and multi-informant analytic techniques to eliminate methodological limitations to understanding the effect of witnessed violence on youth behavioral problems.