Abstract: A conditional process model for the impact of obesity knowledge on healthy food choice was proposed to examine how consumers’ obesity knowledge and online search for nutritional information (OSNI) in food products jointly influenced their healthy food choice (HFC) and whether consumers’ attitude toward health and nutrition-related (HNR) claims in food advertisement directly or indirectly affected their HFC. Results confirmed that OSNI in food products mediated the impact of obesity knowledge on HFC. The extent to which consumers’ obesity knowledge influenced their HFC depended on consumers’ attitude toward HNR claims in food advertisements. Moreover, the conditional direct and indirect effects of consumers’ obesity knowledge on their HFC were moderated by their attitude toward HNR claims in food advertisements. The study offers both theoretical and practical insights into the dynamic effects on HFC via HNR claims in food advertisements.