This study used an experimental approach to examine the influence of message framing and source credibility on potential hotel customers’ attitudes, behavioral intentions, attention, and environmentally friendly activities (EFAs) toward messages about protecting the environment. With 386 participants, this study employed a 2 x 2 between-subject design comparing a positive message frame, a negative message frame, a credible source, and a noncredible source. The results reveal that messages from a credible source that are positively framed led to the most positive attitudes toward the messages themselves, visit intention, and EFAs. Even without regard to source credibility, positively framed messages were more effective than those with a negative frame. The implication for hospitality practitioners is to maintain a positive frame for messages that encourage guests to participate in a hotel’s sustainability programs, and to add a credible source for additional message strength.