BACKGROUND: Greater adherence to dietary guidelines has previously been found to be associated with decreased risk of visual impairment. However, whether or not this association extends to age-related cataract, 1 of the leading causes of visual impairment, is unknown. OBJECTIVES: The aim of this study was to assess the association between adherence to dietary guidelines, using total diet score, and incidence of age-related cataract. METHODS: Of 3654 baseline participants of the population-based Blue Mountains Eye Study cohort (1992-1994), 2334 (75.8% survivors) and 1952 (76.7% survivors) were examined after 5 and 10 y, respectively. Cataract was assessed from lens photographs using the Wisconsin Cataract Grading System. Baseline total diet score was calculated from FFQ data following a modified version of the Healthy Eating Index for Australians. OR with 95% CI were estimated using discrete logistic regression analyses, adjusting for age, sex, and other confounders. To test interaction, a cross-product term of 2 factors was included in regression models. RESULTS: Of 2173 participants (84.7% of those returned for 1 or both follow-ups) with total diet score estimated, 57% were women, mean baseline age was 63.9 ± 8.4y, and mean baseline BMI was 26.3 ± 4.3 kg/m2. After multivariable adjustment, baseline total diet score was not associated with incidence of any cataract. A multiplicative interaction was observed between total diet score and BMI for incident nuclear cataract (P-interaction = 0.04): increasing baseline total diet score was associated with decreased risk of nuclear cataract among participants with BMI <25 (per unit increased total diet score, OR: 0.90; 95% CI: 0.81, 0.99; P = 0.02), but not among participants with BMI ≥25 (OR: 1.00; 95% CI: 0.92, 1.10; P = 0.95). CONCLUSIONS: Adherence to dietary guidelines had no appreciable influence on cataract development overall in this older Australian population. However, adherence to dietary guidelines combined with healthy BMI is associated with decreased risk of nuclear cataract, an aging marker.