Many studies have documented the ways in which shyness can be a barrier to personal well-being and social adjustment throughout childhood and adolescence; however, less is known regarding shyness in emerging adulthood. Shyness as experienced during emerging adulthood may continue to be a risk factor for successful development. The purpose of this study was to compare shy emerging adults with their non-shy peers in (a) internalizing behaviors, (b) externalizing behaviors, and (c) close relationships. Participants included 813 undergraduate students (500 women, 313 men) from a number of locations across the United States. Results showed that relatively shy emerging adults, both men and women, had more internalizing problems (e.g., anxious, depressed, low self-perceptions in multiple domains), engaged in fewer externalizing behaviors (e.g., less frequent drinking), and experienced poorer relationship quality with parents, best friends, and romantic partners than did their non-shy peers.