This chapter examines the impact of posttraumatic stress disorder (PTSD) on family functioning. The chapter reviews multiple empirical studies between 1999 and 2019, highlighting the extent to which different PTSD symptoms of a parent impact both on their partner and more especially on their children. The severity of parental PTSD, particularly emotional numbing and hyperarousal symptoms, significantly increases the risk of physical abuse and emotional neglect of children. Parents experiencing intrusive re-experiencing and avoidance also exhibit emotional neglect and abuse of their children, leading to poor psychological development in offspring. Intimate partner relationships suffer similar deterioration: emotional numbing predicts lower relationship quality, reduced intimacy and heightened conflict and aggression.