The purpose of the research was to examine the effectiveness of Conflict Resolution and Peer Mediation (CRPM) training on high school students' interpersonal conflicts. The CRPM training program was developed by the researchers as a 31-hour program that addressed four basic conflict resolution skills; understanding the nature of interpersonal conflicts, communication skills, anger management skills, and negotiation and peer mediation skills. The study was conducted in a high school located in Izmir, Turkey which served students from low SES families. During the two-year study, a total of 830 students received training, and following the training, 12 peer mediator students were elected from each classroom by their friends. These peer mediators handled their friends' conflicts during three semesters. Data were collected through the peer mediation forms filled by the mediator students following the mediation sessions. A total of 253 mediation sessions were held; 240 (94.9%) resulted in resolution and 13 (5.1%) in no-resolution. Results of the study indicated that CRPM training could prove to be effective in resolving high school students' conflicts.