This study investigates the interdependent nature of corporate communication in sustainability discourse on social media. Using digital trace data from S&P 500 firms' Twitter accounts (2015–2021), we examine how corporations engage in sustainability communication not in isolation, but through patterned and interconnected behaviors shaped by institutional dynamics. We employ the Generalized Connectedness Approach to quantify sector-level interdependencies, revealing strong cross-sector influence in sustainability posting behavior. Based on network position, environmental business orientation, and responsiveness to public attention, we identify four emergent groups of corporations. We then leverage algorithm-supported induction to elicit feature importance, revealing that patterns of sustainability posts, sociopolitical posting, ESG scores, and social media visibility are key predictors of corporate group (i.e., identified in the previous step) membership. We situate these findings within the theoretical lexicon of mimetic isomorphism and organizational routines, arguing that corporate sustainability discourse is shaped by routinized and mimetic communication practices.