The present study investigated the stability of friendship nominations over the course of a school year as a function of early adolescents’ and their classroom best friends’ internalizing symptoms (i.e., depression, anxiety, and somatization). Sample consisted of 156 early adolescents (57.1% female; [Formula: see text] age = 12.62; SD = 0.62) involved in 78 same-sex best friendship dyads. We assessed best friendship (classroom) nominations at beginning (T1) and end (T2) of the school year. Results of longitudinal analyses performed with the Actor-Partner Interdependence Model indicated adolescents’ and their classroom best friends’ depressive symptoms predicted lower stability of best friendships over time, whereas best friends’ somatization emerged as a predictor of higher friendship stability. In addition, positive dyadic friendship quality predicted greater stability over time. These findings highlight the importance of employing a dyadic framework when examining the role of internalizing symptoms in friendship stability.