Background: Non-adherence to prescribed medicines is linked to adverse health outcomes in people living with chronic health conditions (CHCs). Multiple factors are known to contribute to non-adherence to medicines including polypharmacy, demographic features and disease and health systems. Both non-prescription and prescription medicines contribute to polypharmacy; however, there is limited data on the influence of non-prescription medicines to non-adherence. Aim: Therefore, the aim of the study was to investigate the influence of non-prescription medicines to non-adherence in an Australian population. Methods: Data from the 2016 National Survey of a random sample of Australian adult residents were utilised in this study to investigate factors associated with non-adherence. Descriptive statistics, χ2, regression and generalised linear models were used to assess the relationships between variables of interest. Narrative response and comments were used to provide further insight. Results: This study recruited 1217 participants to explore factors associated with non-adherence to medicines. Weak but statistically significant correlations were identified showing the number of CHCs, patient's age, number of prescription medicines, number of non-prescription medicines and total number of medicines associated with non-adherence. Discussion: The findings suggest that people living with CHCs and taking multiple medicines, including non-prescription medicines, are likely to be non-adherent to prescription medicines. This study shows the possible involvement of non-prescription medicines in contributing to non-adherence in an Australian population and suggests that future studies with a broader demographic are warranted.