Companies often encourage consumers to engage in sustainable behaviors using their services in a more environmentally friendly or green way, such as reusing the towels in a hotel or replacing paper bank statements by electronic statements. Sometimes, the option of green service is implied as the default and consumers can opt-out, while in other cases consumers need to explicitly ask (opt-in) for switching to a green service. This research examines the effectiveness of choice architecture and particularly the different default policies-i.e., the alternative the consumer receives if he/she does not explicitly request otherwise-in engaging consumer green behavior. In four experiments, we show that the opt-out default policy is more effective than the opt-in, because it increases anticipated guilt. This effect is stronger for consumers who are less conscious for the environment (Study 1).We also show that a forced choice policy, in which the consumer is not automatically assigned to any condition and is forced to choose between the green and the nongreen service option, is more effective than the opt-in policy and not significantly more effective than the opt-out policy (Study 2). Finally, we show that the role of defaults is weakened (enhanced), if a negotiated (reciprocal) cooperation strategy is used (Study 3). The article contributes to the literature of defaults and provides managerial and public policy implications for the design of green services.