The study explores the differing roles that a top management team (TMT) and a board play in providing a firm the knowledge to improve its absorptive capacity. Building on the distinction between potential and realized absorptive capacity, initially posited by Zahra and George (2002), I argue that a firm's board of directors and its TMT both act to fill the critical role of knowledge gatekeepers identified by Cohen and Levinthal (1990). But, they play different roles in a firm's efforts to acquire, assimilate, transform and exploit novel information. The engagement of board members with environmental planning through personal experiences as well as prior and current ties shapes the ability of the firm to acquire (i.e., identify and obtain) and assimilate (i.e., analyze, understand, and evaluate) valuable external knowledge. However, because they lack the required in-depth knowledge of the firm's internal operations, they are unable to complete the gatekeeping role. The latter stages of that role depend on the abilities of the TMT to transform (i.e., internalize and converse) and exploit (i.e., use and implement) that knowledge, which depends heavily on their engagement with environmental activities through prior experiences. Thus, the board and TMT are only able to fulfill the roles of knowledge gatekeeper collectively. I develop a set of hypotheses from this core proposition, which I test using the participation of U.S. firms in the Carbon Disclosure Project (CDP). Extremely detailed data on 354 firms from 2008 to 2015 allows me to examine multiple sequential processes, including the decision to participate in the CDP performance relative to the core CDP goal, current internal systems, policies as well as plans, and capabilities to breakdown emissions along various production processes to reduce greenhouse gas emissions.