In the face of both increasing climate risks and growing market opportunities, numerous firms are rushing to trumpet their environmental and social achievements. Many firms are, however, seemingly paradoxically, choosing to minimize or withhold their sustainability accomplishments, an increasingly prominent phenomenon known as brownwashing or greenhushing. We draw on an in-depth qualitative study with over 50 firms in the North American wine industry to offer in situ insights on why and how firms engage in brownwashing. Our findings are a significant departure from prior research that has focused on brownwashing to mitigate negative stakeholder judgments. First, our findings reveal firms frequently engage in brownwashing driven by their own judgments of sustainability, specifically its constraints, branding, and community. Second, our analysis reveals the complex interaction between brownwashing and greenwashing and highlights how rampant greenwashing can cause sustainable firms to withdraw green claims, thus considerably advancing the literature on environmental communications. In short, firms are brownwashing because of rampant greenwashing by others. We then develop a foundational model to integrate previously established mechanisms (avoidance brownwashing) with our newly identified mechanisms (rejection brownwashing). As society seeks to engage firms in transparent reporting of sustainability to address grand challenges, our study offers timely theoretical and practical insights.