In this study, we report on the 12-month prevalence of various dimensions of teen dating violence (TDV) victimization and perpetration (emotional, threatening, relational, physical, and sexual) among 9th-grade students in Lower Saxony, Germany. We also present associations between TDV involvement and psychosocial functioning of adolescents (somatic symptoms, psychological symptoms (anxiety/depression, suicidal ideation), and substance use (alcohol and marijuana use). The data stem from a large representative student sample conducted in the year 2015, in which 10,638 9th-grade students were surveyed cross-sectionally. Among these, 4,351 reported having been in a romantic relationship within the 12 months preceding the survey (46.6% male, mean age = 15 years; SD = .76). Results show that 55.6% of the students (girls: 61.8%, boys: 48.5%) reported TDV perpetration, while 56.1% reported TDV victimization (girls: 61.9%, boys: 49.3%) at least once within the previous 12 months. Emotional violence was most frequently reported, while sexual violence was least often perpetrated and experienced. TDV involvement was furthermore significantly related to psychosocial functioning across gender, particularly for victims. The results indicate a significant degree of psychological strain associated with this phenomenon, which calls for the further implementation and dissemination of evidence-based programs that seek to reduce violence in adolescent partnerships.