Despite the developmental relevance and role in social support, research on relationships between adolescents with cancer and healthy peers is limited. To address this gap, we aimed to describe adolescents' perceptions of their friendships during the 1st year following a cancer diagnosis, including relationship changes, factors that promote/inhibit relationships, and definitions and experiences of peer support. Eligible adolescents were 12-20 years old, <1 year of a new cancer diagnosis, and English speaking. Participants completed 1:1 semistructured interviews that were analyzed using inductive content analysis. Fourteen adolescents enrolled and completed interviews (mean [M] = 14.8, standard deviation [SD] = 1.8; M = 6.3 months postdiagnosis, SD = 3.2 months). Domains included (1) shifting relationships, (2) staying connected, (3) making it hard to stay close, and (4) showing me they care. Relationship changes were positive and negative, and many described a process of recognizing true friends. Staying connected with peers through communication, technology, and feeling up to date promoted closeness, while distance, treatment-related restrictions, and friends' discomfort were hindrances. Adolescents defined supportive friends as those who were there for them, checked in often, and gave them gifts. Despite relationship changes, adolescents with cancer desire connection with peers during treatment and perceive that healthy peers provide valuable support. Supporting connectedness to healthy peers during treatment may be a promising future direction to mitigate social disruption and promote well-being.