Although the nutritional and health benefits of buckwheat foods have been widely discussed and evaluated, studies on consumer perceptions of the health benefits of buckwheat functional foods and how these perceived benefits influence their consumption are scarce. On the basis of the theory of planned behavior, this study aimed to explore consumers' purchase intention and behavior toward buckwheat functional foods while assessing the impact of their perceived susceptibility and severity of health concerns on the purchase decisions for such foods. Using data from 1077 participants collected in person from Southwest China, we compared the influencing factors between consumer groups based on whether they were aware of the nutritive and health benefits of buckwheat. The results indicated that, apart from consumers' perceived behavioral control, their perceived susceptibility and perceived severity of three selected common health problems, perceived value and efficacy of buckwheat, and subjective norms were strong predictors of consumers' purchase decisions. Moreover, perceived susceptibility and severity were effective antecedents of the perceived value and efficacy of buckwheat, respectively. Consumers aware of buckwheat's nutritive and health benefits of buckwheat were less affected by perceived efficacy. This study highlights that the higher the susceptibility to the three selected common health problems, the greater the internal and behavioral changes toward the purchase of buckwheat functional foods. These findings reveal factors affecting consumers' healthy eating beliefs, which can be beneficial for both policymakers and marketers in formulating healthy diet policies and strategies in developing countries.