Service providers frequently use pronouns to enhance communication effectiveness and build stronger relationships with their customers. However, the tourism literature is silent on the effect of pronouns in sustainable tourism marketing messages. Drawing on congruity theory, this research addresses this gap by exploring the role of first-person pronouns (i.e., singular vs. plural) in promoting travelers’ pro-environmental behavioral intention. Study one indicates that under the communal relationship norm, sustainable messages using first-person singular (vs. plural) pronouns can generate higher levels of pro-environmental behavioral intention, whereas sustainable messages adopting first-person plural (vs. singular) pronouns are more persuasive under the exchange relationship norm. Study two indicates that for personal hosts, sustainable messages using singular (vs. plural) first-person pronouns lead to higher levels of pro-environmental behavioral intention, whereas sustainable messages using plural (vs. singular) first-person pronouns are more effective for commercial hosts. Furthermore, perceived message appropriateness and warm glow are identified as the underlying mechanisms explaining these effects. Our findings guide tourism practitioners to promote customers’ pro-environmental behaviors by using personal pronouns in sustainable messages.