Background and Aims: Peer relationships during adolescence play an important role in shaping academic outcomes. The present study examined friend influences on emotions towards math, as well as the role of temperament in these influences. Sample: The sample consisted of 350 Finnish students (mean age 13.29 years; 64% girls) who were involved in stable friendship dyads from fall to spring of Grade 7. Methods: In this two-wave study, information on adolescents' temperament (i.e., negative emotionality, extraversion, effortful control) and on seven emotions towards math (i.e., enjoyment, hope, pride, anger, anxiety, shame, hopelessness, and boredom) was collected during grade 7. The data were analysed using longitudinal actor-partner interdependence models. Results: The results showed that friends resembled each other in all the investigated math-related emotions. Furthermore, over and above these initial similarities, friends mutually influenced each other's math-related enjoyment and anger towards math. Students characterized by higher negative emotionality also influenced their friends with lower levels of negative emotionality towards an increase in math-related anger and a lack of effortful control made adolescents more susceptible to friend influence over math-related shame and anxiety. Conclusion: Our findings demonstrate that friends influence each other over time in math-related enjoyment and frustration. Furthermore, high negative emotionality may make adolescents more influential over their friends' math-related anger and a lack of effortful control may make adolescents more susceptible to friend influence over math-related shame and anxiety. Thus, the current findings have implications for how peer relations may impact individual outcomes in mathematics, for better or worse.