This study investigated whether and how classroom-level bullies' friendship networks, which reflect the popularity of bullies, were associated with the self-esteem of middle school students in the classroom. We analyzed survey data from 2,444 students in 101 classrooms from 22 middle schools in Korea. Respondents reported their friends' and bullies' names from their classroom. For each student, we generated the number of close friends that a respondent reported (outdegree) and the number of classmates who nominated him or her as a close friend (indegree). Bullies' popularity was measured by the sum of all the bullies' indegrees in a classroom. The findings showed that students in a classroom of bullies with larger popularity had a lower level of self-esteem. Moreover, bullies' popularity was harmful to nonvictims' self-esteem as well as victims' self-esteem. This study suggests that even indirect exposure to bullying in a classroom can decrease the self-esteem of nonvictims by leading to negative emotions such as anger, anxiety, fear, and/or guilty feelings.