This is an ongoing research project on the issue of prisoners during the Crusades. There is an evident lack of information in the sources on this issue, scarcity of modern scholarship on the subject and inconsistency of the reports written in the primary sources. The researcher was able to gather enough information to try to present a comprehensive synthesis on the subject. The study first attempts to define the principles that regulate the issue of prisoners in both Islam and Christianity, and show how these principles changed during the Crusades. Then, I discuss how prisoners were captured on both sides, the way they were treated and the status of different categories of prisoners, such as women and leaders mainly from among the Crusaders. Finally, I argue that both foes were influenced by the practices of the other party concerning the prisoners of war. The Crusaders learned the benefits of not killing prisoners; ransoming them or enslaving them for labor purposes. On the other hand, the Muslims began to imitate the cruelty towards prisoners just like the Crusaders used to do in the early period of the Crusades.