Pragmatic language difficulties of adolescents with autism spectrum disorder (ASD) can significantly impact their ability to engage in socially appropriate conversations and form peer relationships. Using a multiple baseline design across participants, this study evaluated the effects of a novel peer-mediated intervention (PMI) on improving the social conversation of three high school students with ASD who engaged in high rates of inappropriate communication acts (e.g., perseveration, abrupt topic shifts). The PMI incorporated peer training, graphic/text cues and direct instruction for the students to reduce inappropriate communications while supporting appropriate initiations and topic maintenance responses. Results revealed that the PMI was highly effective in reducing the inappropriate communication acts of three students and increasing the appropriate communication acts of two students. Conversation gains generalized to untrained peers for all student participants. Social validity outcomes assessing intervention acceptability and conversation were highly positive. This study provides additional evidence that PMI can be individualized to address the unique pragmatic language needs of high school students with ASD.