Recently, the number of Instagram users is increasing and the marketing strategy of fashion brands to utilize hashtags (#) is rapidly growing. This study investigates the effects of hashtags in fashion-Instagram on consumer attitudes. The purpose of this study is to investigate the effect of the number, language, and relevance of the hashtags used in fashion-Instagram on the cognitive, emotional, and behavioral factors of consumer attitudes. The results of this study are as follows: First, a lesser number of hashtags has a positive effect on these factors. Second, when the language of the hashtag is English rather than Korean, it has a positive effect on the abovementioned factors. Third, when there is a relationship between the hashtag and the post, the consumers showed significantly more positive attitudes. Therefore, this study can help fashion brands to more effectively utilize hashtags in marketing using Instagram. In addition, this study will likely lead to the development of methods for utilizing hashtags as a more specific means of marketing through future studies.