In this paper, we present the current knowledge on earthworm diversity and zoogeography of Yildiz (Strandja) Mountain in Bulgaria and Turkey. During the investigation in 2015 and 2016, 8 earthworm species altogether were registered. Murchieona minuscula proved to be new to the earthworm fauna of Bulgaria. In addition, there were 4 taxa recorded for the first time from Yildiz (Strandja) Mountain: Aporrectodea jassyensis, Aporrectodea rosea, Octolasion lacteum, and Proctodrilus tuberculatus. Using all existing information on the earthworms from Yildiz (Strandja) Mountain, we summarized our and previously published data and established a list for the whole territory of the mountain from both Bulgaria and Turkey. The list provides information about earthworm diversity, distribution, and zoogeographical position. Currently, 16 taxa belonging to 11 genera are known from the investigation area. According to the zoogeographic position, the largest number of earthworms belong to peregrine, endemic to Bulgaria, Mediterranean, and Trans-Aegean species.