In this article the author presents characteristic features of nineteenth century Tykocin dialect reconstructed on the basis of Dictionary of folk dialects of Tykocin area by Zygmunt Gloger. It results from the analysis of the material that the subject dialect is dominated by features characteristic of Mazovia dialect, e.g. mixing I, y; alternation ke, ge || kie, gie, mazuria “speaking”. Other phenomena, of wider north Polish range occur as well, e.g. shifting of vocal ja- into je-, ra- into re-; e shifting into o when it is a part of the eł group continuing original soft sonant l, -ar- deriving from dispalatized soft sonant r shifting into -er-. Features characteristic of Polish Belarus Borderland dialect, e.g. lack of difference between light a and sloping a, appearance of r instead of rz, substituting ń with n, occur in the Tykocin dialect as well.