A pneumatic tire has an asymmetric tread pattern and an outboard tread edge and an inboard tread edge to be located outside and inside of a vehicle respectively. Inboard shoulder blocks have an axial width and outboard shoulder blocks have an axial width more than the axial width of the inboard shoulder blocks. The inboard and outboard shoulder blocks are each provided with a plurality of sipes. The sipes of each outboard shoulder block include a circumferential sipe as the axially outermost sipe. The circumferential sipe extends at an angle of not more than 10 degrees with respect to the tire circumferential direction. The outboard shoulder block has an axially outer sidewall of which surface is provided with a plurality of narrow buttress grooves extending radially inwardly from the outboard tread edge.