Marketing strategies within retail food environments can be modified to shift customers toward healthier food and beverage purchasing, though customer-level factors, such as shopping behaviour and demographics, may mediate their impact. Healthy Stores 2020 (HS2020) was a 12-13 week randomised controlled trial, conducted in partnership with an Aboriginal-owned organisation managing food retail stores in remote communities, that successfully reduced retailer merchandising and store-level purchases of unhealthy foods through a multi-component strategy (1). However, evidence on how customer-level factors influence food purchases in the context of a health promoting food retail intervention is limited. This study of secondary outcomes from HS2020 aimed to determine: 1) Customer-level factors associated with no discretionary, and no free sugar purchases within a food shop; and 2) whether these factors modified response to the HS2020 strategy. All procedures were guided by the Arnhem Land Progress Aboriginal Corporation and participating communities. A customer intercept survey with collection of transaction data was conducted across 20 participating stores (10 HS2020 strategy; 10 control) during the final two weeks of the trial (December 2018). The survey collected demographics, shopping with/without children, impulse shopping propensity, and payment method. Number of items purchased and dollars spent on discretionary and free sugar products were obtained by linking receipts to a food composition database. Robust Poisson regression models estimated associations between outcomes (discretionary and free sugar purchases per transaction), treatment group, and customer-level factors, with interaction terms to assess effect modification. Statistical significance was set at p<0.01. The analysis included 783 participants – 87.4% Aboriginal and/or Torres Strait Islander. Participants aged ≥ 35 versus < 35 years had a statistically significant higher likelihood of no discretionary purchases (RR = 1.52, 95% CI [1.19, 1.95]) and no free sugar purchases (RR = 1.36, 95% CI [1.36, 2.26]). Low impulsive shopping behaviour also significantly increased the likelihood of making no discretionary purchases (did not buy extras: RR = 1.46, 95% CI [1.18,1.80]), and no free sugar purchases (did not buy extras: RR = 1.70, 95% CI [1.27, 2.29]; decided quickly: RR = 1.51, 95% CI [1.11, 2.05]). Shopping in HS2020 strategy stores and shopping without children were suggestively protective, though non-significant. Several groups showed a suggested association with no free sugar purchasing with the HS2020 strategy compared to controls, including both age categories, cash users, females, those shopping without children, and impulsive shopping behaviours, although none reached statistical significance of p <0.01. Our findings reinforce the benefit of in-store multi-component restrictions on the marketing of unhealthy foods, however broader government regulations on marketing may be required beyond the retail environment to effectively protect younger shoppers, impulsive buyers, and adults shopping with children. Trial Registration: Australian New Zealand Clinical Trials Registry, ACTRN12618001588280.