Scant research on food advertising and purchase decisions has examined the moderating role of social constructs such as power. In this research, I investigate how consumers’ sense of power influences the persuasiveness of message assertiveness in food advertising. The agentic–communal framework of sense of power and findings suggests that high-power individuals are more likely to adopt and be receptive to strong, competent information and communication strategies than low-power individuals in interpersonal communication. In this research, I propose a new theoretical framework that predicts how message recipients’ sense of power enables or weakens the persuasiveness of the assertive message such as, “You must buy [the name of the advertised food].” More specifically, I looked at the likelihood of purchasing ‘vice’ versus ‘virtue' foods after viewing the ad. I argue that for high-power individuals, an assertive tone in the food ads would increase the purchase of a vice food and decrease the purchase intent of a virtue food. However, for low-power individuals, an assertive tone in the food ads would decrease the purchase of a vice food but increase the purchase intent of a virtue food. Low power is less congruent with assertive messages but more congruent with non-assertive messages. Across three studies, I provide empirical support for the predictions and the congruence mechanism. The results show that high-power consumers process assertive messages more fluently than non-assertive messages. Low-power consumers process assertive messages less fluently than non-assertive messages. Processing fluency increases the relative focus on tastiness in food evaluation, but process dis-fluency increases the relative focus on healthiness in food evaluation. The findings of this research have important implications for developing effective marketing communications and promoting healthy eating.