Studies suggest that individuals with schizophrenia have smaller social networks and less satisfying relationships. However, much is still unknown about the typical quantity and quality of social relationships in young adults during the ultra high-risk (UHR) period. Investigating these relationships holds significant importance for improving understanding of etiological processes, mapping the social environment, and highlighting treatment targets in a critical period. A total of 85 participants (44 UHR and 41 healthy controls) completed measures examining the participants’ social relationships, social support, and loneliness. Mean differences between the UHR and healthy control participants and associations between social relationships and symptoms and functioning were examined. Results indicated significant differences between groups on several indices. Specifically, the UHR youth reported fewer close friends, less diverse social networks, less perceived social support, poorer relationship quality with family and friends, and more loneliness. Notably, within the UHR group, being lonely and having fewer and worse quality relationships was associated with greater symptom severity and lower overall functioning. This study suggests that youth at high-risk of developing psychosis have fewer and poorer quality social relationships. Interventions that focus on increasing the quantity and quality of young adults’ social networks may be beneficial for this population.