To estimate the prevalence of drug use before admission to juvenile detention centers (JDC) in Peru and determine individual, family and social influences on behavior. A cross-sectional analysis was performed using data from the 2016 National Population Census in Juvenile Detention Centers (NPCJDC). A total of 1960 Peruvian adolescent offenders were included. Generalized linear models of the Poisson family with a log link function were used to determine if characteristics before admission to a JDC were associated with drug use. These characteristics included employment, depression, neighborhood gang activity, having friends with a criminal record, a history of multiple admissions to a JDC, a history of running away from home, physical abuse during childhood and family history of drug use and incarceration. More than half of young offenders reported using drugs before entering a JDC (59%) in Peru. The drug most frequently consumed was cannabis (86.6%), followed by cocaine and/or crack (11.6%), and inhalants and/or pills (1.8%). Smoking cigarettes [prevalence ratios (PR): 1.12, p = 0.003], using alcohol (PR: 1.22, p = 0.003), neighborhood gang activity (PR: 1.28, p < 0.001), having friends with a criminal record (PR: 1.62, p < 0.001), running away from home (PR: 1.20, p < 0.001) and a family history of incarceration (PR: 1.09, p = 0.010) were associated with drug use prior to admission to a JDC. Drug use before admission to a JDC was high among young offenders in Peru, with marijuana being the drug most frequently used. Having friends with a criminal record and neighborhood gang activity had the greatest association with drug use in young offenders.