This study investigates the history and status of Al-Khadhraa' Mosque in the old city of Nablus, This mosque dates back to the Mamluk period. This study talked about three themes. In the first theme, the researcher talked about the location of the mosque, its date of building and its architectural divisions; in the second theme, he discussed the Awqaf of the mosque, the divisions of these Awqaf and their management, resources and expenses; and in the third theme, he talked about the encroachments on this mosque and its waqf lands. Such encroachments are two types: public encroachments the first of which is the Israeli occupation; and the private encroachments by some citizens of Nablus City who dominated a great part of its waqf land. The study depended on field visits to the site, personal interviews with concerned people, the files of the Awqaf, the records of Sharia Courts and on what the Muslim travelers wrote about the mosque.