Supplements have been growing in popularity among urban consumers due to a perceived lack of sufficient nutrition for good health, with little or no fresh fruits and vegetables now being consumed compared to in the past. In addition, supplements offer consumers the added convenience of obtaining a sufficient amount of nutrition without changing their eating habits. In today’s marketplace, there are many kinds of supplements, such as vitamins, minerals, amino acids, fatty acids, herbs and herbal extracts, and animal extracts. Garlic is a herb grown around the world and one of the most popular due to its numerous benefits. The major aim of this study is to investigate the factors affecting the purchase intention of garlicbased supplements with a higher Allicin content among Thai consumers. In this study, quantitative research was carried out through an online questionnaire survey involving 400 Thai consumer respondents. The results suggest that product knowledge significantly influences the attitude of respondents toward Allicin supplements, while health consciousness had no significant influence. Furthermore, the results suggest subjective norms and perceived behavioral control positively influence the attitude of respondents toward their intention to purchase garlic-based supplements with a higher level of Allicin.