Recently, brand authenticity has emerged as an important factor in consumer purchasing, and many companies are utilizing brand authenticity as a key positioning strategy. According to prior research, brand authenticity encompasses various attributes such as truthfulness, consistency in value delivery, customer orientation, and low commercialism, and its effects operate in combination with other brand factors. This study focused on the variables that mediate the effects of brand authenticity: "consumers' perceived reduction in temporal, financial, and cognitive effort invested in brand purchasing due to authenticity perception" and "trust in the brand." In particular, based on prior research suggesting that perceiving low effort in the selection process of an object leads to enhanced trust in that object, this study aimed to examine the effect of perceived effort reduction in brand information search, processing, and selection on enhancing brand trust. Through this, the study ultimately verified whether the effect of brand authenticity is mediated by "the process through which effort reduction enhances brand trust." In the experiment, fictitious brand advertisements and consumer reviews in which authenticity was either highlighted or controlled were presented, and the perceived degree of effort reduction expected when choosing this brand and trust in the brand were measured, with word-of-mouth and purchase intention for the brand examined as dependent variables. As a result, participants responded that the high-authenticity (vs. controlled) brand would reduce their effort more, which led to higher trust in that brand, ultimately resulting in higher word-of-mouth and purchase intention for the brand. Meanwhile, comparing the magnitudes of indirect effects through contrast analysis revealed that the pathway through which brand authenticity positively affects consumer responses was more powerfully mediated by "the process through which effort reduction enhances brand trust" than by brand trust alone. In conclusion, this study found that the variable of consumer effort reduction plays a highly meaningful role in brand authenticity eliciting favorable consumer responses. Based on the experimental results, the academic significance and practical implications of this study were discussed, and finally, suggestions and directions for future research were presented.