Arthritis is a significant cause of chronic pain and disability, affecting around 3.5 million Australians. However, little is known regarding the overall diet quality of those living with arthritis. This study aimed to assess the dietary quality of Australians living in the Australian Capital Territory region with arthritis. This cross-sectional study analysed dietary intake data of individuals living with arthritis using a validated food frequency questionnaire. Dietary quality was assessed using the Healthy Eating Index-2015 (HEI-2015) to examine associations between diet composition, age, income and arthritis impact using the short form of the Arthritis Impact Measurement Scales 2 (AIMS2-SF). Participants, predominantly female (82.6%), were grouped by age: 18-50 years (n = 32), 50-64 years (n = 31), and 65 + years (n = 23). Significant correlations were observed between age and HEI-2015 (rs = 0.337, p = 0.002) and income and AIMS2-SF (rs = - 0.353, p < 0.001). The mean HEI-2015 score for the 18-49 years group was fair (72.1 ± 12.3), lower than both the 50-64 years group score of good (81.5 ± 9.72) (p = 0.004), and the 65 + years group score of good (81.8 ± 12.1) (p = 0.007). Dietary fibre, seafood and plant protein, fatty acids, and refined grains were identified as dietary components of concern for the 18-49 years group, and total fruit and added sugar were components of concern for people in the worst tertile for the AIMS2-SF. People aged between 18 and 49 years are consuming a lower quality diet compared to people aged 50 years and over. Further research is needed to understand why this association is occurring in this high socioeconomic region of Australia (a high-income country).