A syndiotactic polystyrene composition is improved which exhibits improved crystallization rate. The improved syndiotactic polystyrene composition contains (a) a syndiotactic polystyrene; and (b) a nucleating agent which is selected from the group consisting of two types of compounds represented by the following formulas, respectively: ##STR1## In Formulas I and II, the radicals R.sub.1 and R.sub.2, which can be the same of different, are C.sub.1 to C.sub.5 alkyl groups, X is a halogen group, preferably a bromide group, and n is an integer from 1 to 5. In the present invention, the nucleating agent is provided at 0.01 to 5 part, by weight, per 100 parts, also by weight, of the syndiotactic polystyrene resin. An example of Formula I compound is 2-hydroxybenimidiazole, and an example of the Formula II compound is bis(phenylbromide) methane.