Children's exposure to intimate partner violence (IPV) is a prevalent public health problem that can result in serious mental health impairments, including traumatic stress. These can emerge early and persist across development. IPV early in life has also been described as a "gateway exposure" to other forms of adversity and trauma. Children and families impacted by IPV have complex needs that complicate assessment and intervention. This paper highlights these issues and reviews best practices in assessment, case conceptualization, and treatment planning as they pertain to the treatment of IPV-exposed children. A case vignette illustrates the complex nature of IPV and application of best practices by telling the story of Isaiah, a 13-year-old boy with an extensive history of IPV exposure and co-occurring adversity and trauma.