To examine the prevalence and magnitude of price promotions in a major Australian supermarket and how they differ between core (healthy) and discretionary (less healthy) food categories. Weekly online price data (regular retail price, discount price, and promotion type) on 1579 foods were collected for 1 year (April 2017 to April 2018) from the largest Australian supermarket chain. Products audited were classified according to Australian Dietary Guidelines definitions of core and discretionary foods and according to their Health Star Rating (a government-endorsed nutrient profiling scheme). On average, 15.1% (95% confidence interval [CI] = 14.7%, 15.3%) of core foods and 28.8% (95% CI = 28.6%, 29.0%) of discretionary foods were price promoted during a given week. Average discounts were -15.4% (95% CI = -16.4, -14.4) for core products and -25.9% (95% CI = -26.8, -25.1) for discretionary products. The percentage of products on price promotion and the size of the discount were larger for products with a lower Health Star Rating ( < .05). Price promotions were more prevalent and greater in magnitude for discretionary foods than for core foods. Policies to reduce the prevalence and magnitude of price promotions on discretionary foods could improve the healthiness of food purchased from supermarkets.