The present invention provides a rubber composition that allows uniform dispersion of microfibrillated plant fibers so as to improve the required performance for a tire in a balanced manner, and a pneumatic tire formed from the rubber composition. The present invention relates to a rubber composition prepared from a masterbatch obtained by mixing rubber latex, microfibrillated plant fibers and a cationic polymer, wherein 0.01 to 5 parts by mass of the cationic polymer is added per 100 parts by mass of a rubber component of the rubber latex.