Aim: The aim of this study was to examine the relationships of food security and diet quality with health related quality of life (HRQoL) in a cohort of older Australians. Methods: Data were collected as part of the Blue Mountains Eye Study, a cohort study of community-living individuals aged 49 years and over. A 12-item food security survey, the Short-form 36-item (SF-36) health survey, assessing four physical and four mental domains of HRQoL, and a food frequency questionnaire (FFQ) were completed by 2642 participants. The Total Diet Score (TDS) (maximum score 20) measured diet quality based on food intake from the FFQ. Analysis of covariance compared adjusted mean differences in SF-36 scores between (i) food secure and food insecure groups and (ii) quartiles of TDS. Higher SF-36 scores indicated better physical and mental health. Results: Across all SF-36, domains scores were significantly lower in the food insecure group compared to the food secure group. Adjusted mean differences ranged from 4.01 (95% confidence intervals (CIs): 1.64, 6.38) to 18.00 (95% CIs: 13.43, 22.56). Individuals in the lowest quartile of TDS had significantly lower SF-36 scores compared to those in the highest TDS quartile for physical functioning domain (4.46, 95% CIs: 1.67, 7.26) and vitality domain (4.14, 95% CIs: 1.34, 6.95). Conclusions: The study findings provide evidence of associations between reduced physical and mental health and food insecurity and poor diet quality, respectively. Further research into food insecurity in the ageing population is required to ensure that good health is maintained through appropriate health and community services.