Friendships are important for the mental well-being of emerging adults. Socially prescribed perfectionism, where individuals feel pressured to be perfect by others, can be destructive, leading to conflict with others, depressive symptoms, and problematic drinking. However, its impact on friendships is not well-explored. This study examined 174 emerging adult friendship dyads using a 4-wave, 4-month dyadic design. Data were analyzed using longitudinal actor-partner interdependence models. Using a novel friend-specific measure of socially prescribed perfectionism, we found that an individual's perceived expectation to be perfect from a friend was positively associated with increased conflict between friends, as well as with higher levels of depressive symptoms and problematic drinking in the individual. Findings lend credence to longstanding theoretical accounts and case histories suggesting socially prescribed perfectionism leads to harmful individual and relational outcomes and extends them to the specific context of friendships.