Indo-European languages have been spoken in the Caucasus over millenia, alongside languages of the three indigenous families of the region. This chapter provides a general overview of four languages whose core area is situated in the Caucasus (both the North Caucasus and Transcaucasia): Eastern Armenian (which together with Western Armenian forms a separate branch of Indo-European) and three Iranian languages: Ossetic, spoken in North Ossetia, part of Russia, and South Ossetia beyond the mountain range; Judeo-Tat, spoken by Mountain Jews in Dagestan and Azerbaijan; and Talyshi, spoken by the Talysh people mainly in the south of Azerbaijan, but also in neighboring regions of Iran. The chapter captures the current understanding of the core areas of phonology and grammar of these languages and provides information on features that could possibly have been induced by contact with the neighboring Caucasian languages.