This work compares the use of palace diplomacy and propaganda by the rulers of Constantinople and Mexico-Tenochtitlan. It builds on studies of the cultural exchange between the Roman and Sasanian empires from the third to sixth centuries a.d., which led to a diplomatic protocol shared by these two realms. This protocol and Liudprand of Cremona’s account of diplomatic receptions are the basis for comparative analysis. Drawing on Hernando Alvarado Tezozómoc’s Crónica Mexicana and other sixteenth-century sources, this study identifies key characteristics of diplomacy in Mesoamerica. It explores how Mexico-Tenochtitlan employed palace diplomacy and propaganda from the reign of Motecuhzoma Ilhuicamina to Motecuhzoma Xocoyotzin. Through this analysis, we find that the diplomatic and propaganda objectives of Constantinople and Mexico-Tenochtitlan had distinct focuses. The Byzantine rulers aimed to maintain their existing empire, while the Tenochca rulers sought not only to preserve but also to expand their domain. As a result, Constantinople’s strategy emphasized palace diplomacy, whereas Mexico-Tenochtitlan’s focused more on propaganda. Despite these differences, both approaches share several similarities. Both began with invitations, and their protocols included the same components: visual (architecture, wealth, and terror), ceremonial (including aural, olfactory, gustatory, ludic, haptic, somatic, and terror elements), and diplomatic (interviews and gift exchanges).