Objective: The prevalence of childhood abuse among injection drug users (IDUs) in San Diego, California, is unknown. The objective of this study was to identify correlates of childhood abuse among current IDUs and investigate the relationship between childhood abuse and Hepatitis C (HCV) infection. Methods: IDUs greater than 18 years of age who had injected drugs in the previous three months were recruited using three methods from 2009-2010, and completed a behavioral assessment and testing for HIV and HCV. Bivariate and multivariable logistic regression was used to determine correlates of childhood abuse and correlates of HCV. Results: Of 489 IDUs, 45.8% (n=224) reported a history of childhood abuse. Almost a quarter of IDUs reported a history of both physical and sexual abuse in childhood (22.7%, n=111), 88 (18.0%) reported a history of physical abuse only in childhood, and 25 (5.1%) reported a history of sexual abuse only in childhood. IDUs with a history of both physical and sexual abuse in childhood, and a history of physical abuse only in childhood, had riskier drug-injection practices than their non-abused IDU peers. IDUs with a history of both physical and sexual abuse in childhood were more likely (unadjusted OR=1.67, 95% CI: 1.03, 2.70) to be HCV-positive than their non-abused peers. Factors independently associated with HCV infection included: injecting with strangers or acquaintances compared to always alone in the last 3 months (AOR=0.42, 95% CI: 0.20, 0.87), duration of injecting (AOR=1.11, 95% CI: 1.07, 1.15), a history of overdose (AOR=2.84, 95% CI: 1.71, 4.70), injecting at least daily in the last 3 months (AOR=2.53, 95% CI: 1.57, 4.09), sharing injection paraphernalia in the last 3 months (AOR=2.11, 95% CI: 1.96, 3.74), having a legal source of income other than a regular job (AOR=2.53, 95% CI: 1.30, 4.95), and having an illegal source of income other than a regular job (AOR=2.42, 95% CI: 1.02, 5.78). Conclusions: Findings show that almost half of IDUs ages 18-40 years in San Diego have a history of childhood abuse, and that IDUs with a history of childhood abuse are a particularly vulnerable and marginalized population. IDUs with a history of abuse practice risky drug injection practices and have markers of vulnerability above and beyond an already high-risk group (their non-abused IDU peers). The findings suggest that people who work with IDUs may be better able to serve them if they address the IDU's history of childhood abuse, along with messages of safe injecting practices. IDUs in drug treatment centers should be screened for childhood abuse, as an integrated approach addressing the entire personhood of the IDU may be more effective in helping IDUs battle their addictions and preventing the spread of HCV in the IDU community.