A growing consensus suggests that incarcerating offenders tends to have either null or criminogenic effects at both the individual and neighborhood levels. There is also further evidence that there are unintended consequences of incarcerating juvenile offenders such as delayed psychosocial development and school dropout. The current study considers a much less examined hypothesis — that correctional environments can facilitate the accumulation of “criminal capital” and might actually encourage offending by serving as a school of crime. Using unique panel data from a sample of serious juvenile offenders, we are able to identify the criminal capital effect by considering illegal earnings and information regarding institutional stays over a seven year period. We have two separate measures that tap into the different mechanisms by which offenders can acquire criminal capital within institutions: the prevalence of friends in the facility who have committed income generating crimes and the length of institutional stays as a cumulative dosage. We find that both facility measures have independent positive effects on an individual’s daily illegal wage rate, even after controlling for important time varying covariates. Theoretical and policy implications are discussed