The current study investigated early adolescents' experiences of friend-related stress across middle school and its developmental consequences following the transition to high school. Using a sample of approximately 1,000 middle school students, four unique friend-related stress trajectories were observed across middle school: consistently low friend-related stress (57% of the sample), consistently high friend-related stress (7%), moderate and increasing friend-related stress (22%), and moderate but decreasing friend-related stress (14%). Groups characterized by higher levels of friend-related stress across middle school were linked to subsequent poorer socioemotional well-being, lower academic engagement, and greater involvement in and expectancies around risky behaviors following the transition to high school. Increased friend-related stress across the high school transition was also linked to poorer outcomes, even after taking into account earlier stress trajectories. Gender differences highlighted the particular struggles girls experience both in friend stress and in the links between friend stress and subsequent well-being.