This panoramic historical study deals with varied kinds of interaction between Tajik language and vernacular Northern Iranian languages in the Autonomous Region of Higher Badakhshan (Tajikistan). Paragraphs on the history of Tajik language during the Soviet period are followed by considerations on the impact that migrations of agricultural manpower from the Yazghulami and Wakhi ethnic groups towards Tajikistan’s southern lowlands, from the 1950s onwards, had on the appearance of local Tajik sub-dialects, and on the latter’s diffusion towards Badakhshan after the temporary return of these migrant populations to their native places during the civil war of the 1990s. Local Tajik dialects have Pamir languages as a substratum, and as such fall under their influence; this influence is particularly evident in phonetics, vocabulary, and syntax. Apart from these variants of Tajik in Badakhshan, the author also devotes some pages to the special Tajik dialect (called “parsi” or “farsi”) that is used locally as intermediate language between Tajik and Pamiri populations. Recently, the current Isma‘ili revival in Badakhshan has reinforced the prestige and direct influence of Persian language, that has been in some places implemented as a foreign language in schools, on the basis of the Arabic script. However, beyond the author’s romantic view of a Persian revival, such a trend remains very limited, and is to be put in perspective with concurrent Isma‘ili religious influences coming, notably, from the Indian subcontinent.