Social connections are essential to health and well-being. However, when pursing social acceptance, people may sometimes engage in behavior that is detrimental to their health. Using a multi-time-point design, we examined whether the structure of an emerging network of students in an academic summer school program correlated with their physical health and mental well-being. Participants who were more central in the network typically experienced greater symptoms of illness (e.g., cold/flu symptoms), engaged in riskier health behaviors (e.g., binge drinking), and had higher physiological reactivity to a stressor. At the same time, they were happier, felt more efficacious, and perceived less stress in response to a strenuous math task. These outcomes suggest that social ties in an emerging network are associated with better mental well-being, but also with poorer physical health and health behaviors.