Despite the prevalence of celebrity endorsers for brands that feature sustainable products, there are few empirical studies on what factors should be considered in utilizing endorsers in marketing sustainable products. In this study, we explored the relationships between celebrity endorsers’ characteristics and consumers’ perceptions, attitudes, and purchase intentions toward a brand that markets sustainable products. The data were collected via an online survey with a total of 1,220 responses, and structural equation modeling was used to test the hypotheses. In the results, endorser trustworthiness and endorser-brand congruity positively predicted brand credibility while endorser ethicality and endorser-brand congruity positively predicted brand ethicality. Brand ethicality positively predicted brand credibility. Brand credibility positively predicted brand attitude as well as brand purchase intention. Although brand ethicality positively predicted brand attitude, it did not predict brand purchase intention. Lastly, brand attitude positively predicted brand purchase intention. Theoretical and practical implications were discussed.