In recent years, the size of the DHA market has grown rapidly. However, the characteristics of DHA supplement users in Japan are not evident because only a few studies are available on this subject. In this study, we used a survey questionnaire to describe the characteristics of DHA supplement users and nonusers and their reasons for using them. Our results show that more than 50% of DHA supplement users are women aged between 30 and 59 years. They claim to use DHA supplements for maintaining health and not as a substitute for seafood. Therefore, based on our survey results, we propose that the DHA supplement market growth will not affect the seafood market in Japan. We also show that users of DHA supplements consider the brand value, company reputation, and products more than the functional claims of the product. Consumers have less knowledge about selecting DHA supplements； thus, companies must provide them information and guidelines for selecting DHA supplements that provide targeted support.