Abstract Background Almost 60% of Australians report low levels of health literacy (HL). International evidence indicates limited comprehension of the risks and benefits of cardiac surgery, in addition to understanding the basic elements of informed consent. Purpose The aim of this study was to explore HL in adult cardiac surgical candidates. Methods We recruited consecutive English speaking adult patients from a major public (Site 1), major private (Site 2) and regional hospital (Site 3) in Victoria, Australia. Prior to discharge, a Registered Nurse conducted a semi-structured interview using the Health Literacy Questionnaire (HLQ). The HLQ is a multidimensional validated instrument comprised of 9 independent scales. Data were analysed using descriptive statistics, t-tests and ANOVA. Results We recruited 164 (29.5%) eligible participants from; Site 1 (63, 32.1%), Site 2 (49, 19.3%) and Site 3 (52, 49.5%) respectively. Average age was 64.6 (SD 11.8), most participants were male (n = 134, 81.7%), few lived alone (n = 28, 17.1%), 122 (74.4%) identified as being Australian 5 (4.1%) of whom were indigenous and 9 (5.5%) spoke a language other than English at home. The majority of participants highest level of education was aligned with a trade certificate (n = 48, 29.3%) or not completing high school (44, 26.8%) and most were retired (n = 68, 41.5%), working full time (n = 51, 31.1%) or part time (n = 24, 14.6%). Less than half had private insurance (n = 72, 43.9%), more than half had presented to emergency (n = 87, 53.0%) in the previous 12 months and a history of cardiac complaints (n = 137, 83.5%) was as expected. In this study participants felt understood and supported by healthcare providers (Scale 1 M 3.32, SD 0.26), had sufficient information to manage their health (Scale 2 M 3.13, SD 0.35), proactively managed their health (Scale 3 M 2.98, SD 0.39), had strong social supports (Scale 4 M 3.31, SD 0.36), could appraise health information (Scale 5 M 2.88, SD 0.49) and were proactively engaged (Scale 6 M 4.00, SD 0.50). More challenging was their ability to advocate on their own behalf (Scale 7 M 3.80, SD 0.60), to explore information (Scale 8 M 3.70, SD 0.60) and to understand all written information (Scale 9 M 3.90, SD 0.60). Site 2 participants were highly educated, less likely to live alone, more likely to have private insurance, had fewer emergency presentations and higher scores on scales 6 to 9 (p < 0.05) that measure health care interactions, than those from Site 1 or 3. Conclusions There was a high level of HL in this cohort and findings indicate patient strengths in relation to HL differed according to site. In measuring individual skills and experience of participants interacting with services, systems and the health care environment this study provides valuable insight into HL levels in cardiac surgery candidates.