Consumers increasingly expect brands to contribute positively to the environment. This trend has created a race for brands to establish their “green” credentials. Asserting their superiority—a strategy we refer to as an arrogant appeal—may allow some brands to connect with this consumer preference if perceived as credible; however, when this brand communication lacks credibility, consumers lose trust and suspect brands of greenwashing. Applying expectancy violation theory and signaling theory to green advertising, we find a specific message source (level of brand dominance) influences the effectiveness of an arrogant appeal. Specifically, via the use of two experiments, we demonstrate that consumers use market dominance as a cue to establish the credibility of an arrogant appeal. This research (a) builds on comparative advertising literature to introduce the concept of arrogant appeal to the literature, (b) identifies a new credibility signal—brand dominance—for the effectiveness of green advertising appeals, (c) extends marketing research on arrogance to message design and source characteristics, and (d) discusses the ethical ramifications of consumers inferring credibility based on market dominance. A critical finding is that more dominant brands have earned the right to deploy an arrogant appeal based on a consumer heuristic.