Triggered by the conquest of Ceuta in 1415, the Portuguese overseas expansion in the fifteenth century transformed Moroccan coastal areas into frontiers between Christians and Muslims. Scholars often discuss this crucial moment for Morocco from a nationalist and state-centered framework, thereby emphasising the roles of ruling dynasties and their jihad movement as the manifestation of national consciousness. These accounts, however, overlook the diversity and fluidity of reactions that local Muslim communities showed to their new aggressive neighbours. In this paper, I argue that Muslim inhabitants, in fact, adopted what we might call ‘improvised diplomacy’ involving a much wider range of survival strategies from alliance, obedience, escape to armed struggle. It was these diverse strategies and negotiations that conditioned the fragile relationship between the conqueror and the conquered. To develop this perspective, I will begin by investigating the identity of diverse actors, such as tribal chieftains, alfaqueques (captive redeemer), new Christians, and Moriscos, who crossed politico-religious boundaries in the north of the country and participated in these improvised negotiations. In so doing, I will use not only Portuguese chronicles and archival records but also Arabic historical and legal texts concerning this period. The analysis will first enable us to understand the broader formation of inter-religious relationships between Portuguese conquerors and tribal communities near the conquered places, which could hardly have expected the protection from the state. Secondly, I will also demonstrate that their provisional practices not only attenuated the effect of violent situations that characterised the relationships of these antagonistic communities until the middle of the century but also paved the way for a more formal, inter-state diplomacy in the last decades of the century. Finally, I will conclude by stressing the importance of ad-hoc negotiations in understanding the inter-religious relationships of the premodern Western Mediterranean. It will contribute to a recent debate on the history of diplomacy that aims to free it from Eurocentric narratives.