A tubeless pneumatic tire is provided which can sufficiently prevent air leakage from a puncture hole formed through a tread portion of the tire by a nail or the like, while ensuring a desired cushioning performance of the tire during normal operation. The tubeless pneumatic tire includes an annular tread portion, and a pair of sidewall portions extending radially inwardly from laterally opposite sides of the tread portion. An intermediate liner is provided inside of the tread portion, along with a first release sheet on the outer surface of the intermediate liner, and a second release sheet on the inner surface of the intermediate liner. A sealing chamber, for encapsulating a puncture sealant, is further provided inside of the intermediate liner. The puncture sealant may include both fibers and particles, to enhance sealing of the puncture hole.