OBJECTIVE: This study examines the relationship between family processes and youth substance use debuts among a sample of youth residing in urban family homeless shelters. METHOD: Data regarding shelter experiences, youth and family characteristics, and the use of three substances (i.e., cigarettes, alcohol, and marijuana) were gathered from a sample of youth (11-14 years) and their respective parents residing in an urban family homeless shelter system. Multinomial logistic regression analysis was used to examine the influences on youth substance use. RESULTS: Of the 198 youth included in the statistical analysis, 72% (n=143) reported no substance use debuts, while 18% (n=35) indicated one and 10% (n=20) indicated two to three substance use debuts. Within the final model, greater substance use debut was associated with being older (13-14 vs. 11-12; OR=7.5; 95% CI =1.8-30.9) and stressors exposure (OR=4.8; 95% CI =1.5-14.7). Furthermore, youth of adult caretakers that reported low levels of the three family processes considered were almost four and a half more likely (OR=4.4; 95% CI =1.2-16.5) to have made two to three substance use debuts. CONCLUSIONS: Family processes may be a particularly important intervention target toward reducing the rate of substance use among youth residing in urban family homeless shelters.