The present study examines the persuasive effects of green marketing appeals by corporations from industries with highly-publicized histories of environmental disregard, specifically multinational petroleum corporations (MPC’s). Prior research has been done regarding corporate environmental communication and perceived environmental legitimacy, or credibility regarding the firm’s relationship with the environment. Research specifically investigating the persuasive effectiveness of green marketing, however, by traditionally environmentally-unfriendly companies is extremely sparse. It is for this reason that this study attempted to measure audience perceptions of oil companies as credible sources of information. These perceptions were based off appeals by these companies focused on proper interactions with the environment. A secondary focus of the study was an examination of whether or not an audience member’s ego involvement with the environment significantly influences their likelihood of being persuaded by an appeal. The study was conducted with undergraduate students from a small, Midwestern liberal arts university serving as participants and specifically examines whether a televised, environmentally-based advertisement from Chevron Corporation entitled Untapped Energy increased the company’s perceived environmental legitimacy among viewers as well as how viewer involvement factors into this process.