Background: Studies of healthcare service use often rely on self-reported data, especially in disadvantaged populations. Despite this, the reliability of self-reported healthcare service use is often questioned and routinely-collected, administrative data are usually considered preferable. In this paper we examine the agreement between self-reported healthcare service use and administrative records, in a large cohort of adults recently released from prison in Australia. Methods: Baseline interviews within 6 weeks of expected release from prison and follow-up interviews at 1, 3 and 6 months post-release were linked to routinely-collected, administrative health records over the same time period. Outcomes of interest included use of primary care, emergency department presentation, hospitalisation and dispensing of subsidised pharmaceuticals. Kappa statistics and positive and negative predictive values were calculated for each service type and time point, and a modified Poisson regression was used to identify participant characteristics associated with better agreement. Results: 864 participants completed interviews and were successfully linked to administrative records. There was good agreement between self-report and administrative health records. Agreement between data sources at 1 month was best for psychotropic medications (kappa = 0.79) and primary care visits (kappa = 0.69). Conclusion: Despite a common perception that studies using self-reported data are subject to bias, particularly among the disadvantaged, our findings suggest that self-reported healthcare may be valid in vulnerable populations.