This study analyzes the competitive structure of the Korean health functional food (HFF) market using brand switching behavior derived from official market share data.By analyzing data from 2022-2023 provided by the Ministry of Food and Drug Safety.This study applies to the Hendry Model, a probabilistic brand-switching framework.We tested hypothetical market structures based on product categories, health claims, and manufacturers.The findings reveal a segmented market with limited substitution between submarkets.We identified 5 distinct product category submarkets, 4 health claim submarkets, and 3 manufacturer groups.The results suggest that competition in the HFF sector occurs primarily within submarkets rather than across the entire market.Firms should tailor product strategies to the specific dynamics of each segment.This study highlights the value of probabilistic modeling in uncovering latent market structures and informing strategic positioning.