In the current work friction stir processing of the Ti-6Al-4V alloy was carried out. Various process parameters (tool traverse speed and tool rotation speed) were studied for successful FSP of Ti-6Al-4V. The process parameters were identified using macrostructure observation on the surface of processed plate and microstructure evolution in the stir zone (SZ) of the FSP specimen. The effect of tool traverse speed and tool rotation speed on microstructure evolution in the SZ, thermo-mechanically affected zone (TMAZ) and heat affected zone (HAZ) were studied. The microstructure transformation from initial elongated α structure to prior β grains, with α layer grain boundary consisting of mixture of acicular α′ and very fine lamellar α/β colonies, was observed at SZ. This was the case for wide range of variations in parameters except for the tool rotation speed of 600 rpm and traverse speed of 60 and 100 mm/min. Under this combination of parameters, the bands of DRX α and transformed β structure were observed to evolve at SZ. © 2017, The Minerals, Metals & Materials Society.