Toward the end of the Roman Empire, slavery began to decline as slave labor became increasingly scarce and expensive. Although disrupted by the barbarian invasions of the early Middle Ages, slavery continued to exist in western Europe and in the Byzantine Empire. The Christian Church did not oppose the institution of slavery, considering it a part of the divine order of the world. However, the Church asserted the equality of both master and slave before God and sought to mitigate some of the evils of servitude.

As early as the sixth century A. D., slavery in Europe began to be replaced by serfdom, a system that proved better suited to the emerging feudal agricultural economy. Serfs were in a state between slave and free, bound to the soil (that is, they could not leave the land of their own free will) and more or less subject to the will of their lord. However, the religious wars between Christians and Muslims helped to keep slavery alive, as each side enslaved prisoners of the opposing religion. In the late Middle Ages, warfare against the Turks and a demand for domestic servants revitalized slavery for a time in some parts of Europe. The Mediterranean slave trade reached its peak in the 14th and 15th centuries.