The great 13th century scholar Yāqūt al-Hamawī, compiled his well-known geographical dictionary – Mucğam al-Buldān – using an incredibly vast corpus of sources that allowed him to describe the lands lying beyond the realm of Islam. The aim of this paper is to identify the sources he used to describe issues dealing with the Slavs or those peoples and areas thought by Arab writers to belong to or be connected with the Slavs. The results shed some light on the state of knowledge of this area among 13th century inhabitants of the caliphate. At the same time, the author’s analysis of the methods employed to compose the material on the Slavs that appears in the Dictionary helped determine the aim and the role of this work in the caliphate.