Background: Drug injection in prison is associated with a high risk of transmission of blood-borne pathogens including hepatitis C (HCV). The aim of this study was to estimate the prevalence and identify independent correlates of recent in-prison injecting drug use (P-IDU) among a large sample of adult prisoners in Queensland, Australia. Methods: Confidential, structured interviews with 1,322 adult prisoners in Queensland, Australia. Prevalence estimates were corrected for sampling bias using inverse probability weighting. Independent correlates of recent P-IDU were identified using multivariable Poisson regression with backwards elimination. Results: We estimated that among all adult prisoners in Queensland, Australia, the prevalence of lifetime IDU was 55.1%, of lifetime P-IDU 23.0%, and of recent (during current sentence) P-IDU 13.2%. Significant, independent correlates of recent P-IDU included male gender (ARR=3.07, 95%CI 1.83-5.12), being unemployed prior to incarceration (ARR=1.34, 95%CI 1.01-1.76), use of three or more drug types prior to incarceration (ARR=1.80, 95%CI 1.40-2.31), a history of needle/syringe sharing (ARR=5.00, 95%CI 3.06-8.16), receiving a tattoo during the current prison sentence (ARR=2.19, 95%CI 1.67-2.86) and HCV exposure (ARR=1.47, 95%CI 1.08-2.02). Older age was protective (ARR=0.90 per 5 years older, 95%CI 0.83-0.99). Conclusion: Drug injection in prison is common and, given the associations between in-prison drug injection and syringe sharing, unsafe tattooing and HCV exposure, poses a risk to both prisoner health and public health. There remains an urgent need to implement evidence-based infection control measures, including needle and syringe programs, within prison settings.