This paper provides evidence of a novel facet of peer effects by showing that peer personality influences academic achievement.We exploit random assignment of students to university sections and find that students perform better in the presence of persistent peers. The impact of peer persistence is enduring, as students exposed to persistent peers at the beginning of their studies continue to achieve higher grades in subsequent periods. The personality peer effects that we document are distinct from other observable peer characteristics and suggest that peer personality traits affect human capital accumulation.