As students transition into adolescence they are often permitted greater independence in nonclassroom settings within schools and thus the opportunities for problem behaviors increase. However, nonclassroom settings can also provide an opportunity for students and school staff to engage in informal yet positive interactions. This paper aimed to identify potential predictors of observed student behaviors in nonclassroom settings in high schools, such as characteristics of the settings (e.g., location) and observed adult behaviors. Hierarchical analyses were conducted on observational data (N = 917) collected in nonclassroom settings (i.e., arrival/departure, hallway/stairway, and cafeteria) in 58 high schools. Fewer negative student behaviors and increased positive student behaviors were observed when adults actively connected with students. Furthermore, the frequency of negative student behaviors varied by location, time of year, and time of day. This study contributes to prior literature through the focus on nonclassroom settings, examination of adult as well as student behavior, and the use of observational methodology in high schools. Implications for schools seeking to reduce problem behaviors and improve school climate in nonclassroom settings are discussed.