Abstract Background Diet quality positively correlates with socio-economic position (SEP). While nudges are often proposed as promising policy tools for promoting health behavior among lower SEP groups, research addressing their impact within lower SEP groups is limited. This study aimed to 1) examine the efficacy of a checkout repositioning nudge in a supermarket in a deprived area in encouraging purchases of healthier snacks, and 2) describe customers’ preferences and needs regarding grocery shopping and healthy eating. Methods Daily sales data were collected over four-week control and intervention periods. During the intervention, unhealthy snacks at the checkout were replaced by healthier snacks. Additionally, questionnaires were administered among customers (N = 90). Results The intervention led to a significant increase in daily sales of healthier snacks (M = 3.14, SD = 2.45) compared to the control period (M = 0.54, SD = 0.96), t(27) = 5.62, p < .001. Despite a statistically significant nudge-effect, the absolute daily sales of healthier snacks remains extremely low. No difference in daily sales of unhealthy snacks was observed between both periods. Questionnaire data showed that customers report to seldomly purchase snacks at the checkout, find it important to eat healthily, think well about what they buy in a supermarket, and long for a healthier and more affordable food offer within the supermarket. Conclusions Interventions that are effective among higher SEP groups, such as repositioning nudges, may not be suitable for the circumstances and needs of lower SEP groups. To combat existing health inequalities, interventions must be tailored to lower SEP groups. More system-level interventions that target the healthiness and affordability of the offer may be needed. Key messages • Although nudging is often proposed as a promising policy approach for improving health behavior among lower SEP groups, repositioning nudges may not suit their circumstances and needs. • To combat health inequalities, interventions must be tailored to lower SEP groups and integrated with system-level policies (e.g., targeting the healthiness and price of the offer in supermarkets).