Persian surrounds much of the Tabari (or Māzandarāni) speaking area, that is, the province of Māzandarān south of the Caspian Sea. The transition zones between the two languages lay in the valleys and foothills of the Alborz range, which separates Māzandarān from the Iranian Plateau. Within this zone we find a range of hybrid dialects that are divided into two distinct groups: Persian dialects influenced by Tabari and vise versa. This study aims at the latter group, which we call Tabaroid, i.e., Tabari varieties carrying various amounts of Persian mix. The linguistic data come from some twenty villages in the south-central Alborz, separated from Tehran by a mountain ridge. The main objective here is to establish the dialectal and areal position of the Tabaroid varieties by closely examining their diachrony, phonology, and above all morphosyntax.