Side chain of syndiotactic-1,2-polybutadiene (SPBU) has been modified by means of hydrogenation, hydrosilylation with trialkylsilane compounds, or thiol-ene reaction with alkyl thiol compounds. Crystallization temperature (T-c) of the resulting polymers, which was detected on the cooling process from melting state, decreased with increasing the modification ratio. The molecular bulkiness of the compounds affected the degree of the T-c depression with increasing the modification ratio. The modification of SPBU with triphenyl silane increased glass transition temperature of the polymers. Isothermally crystallized SPBU samples modified by butane thiol (BT) showed two melting peaks derived from first crystallization (T-m1, higher temperature) and second crystallization (T-m2, lower temperature). The T-m1 decreased with increasing the modification ratio, whereas the T-m2 was almost independent of the modification ratio. The equilibrium melting temperatures of the T(m1)s of the SPBU samples modified by BT were decreased with increasing the modification ratio. By contrast, the modification ratio did not affect the equilibrium melting temperatures of the T(m2)s. Slopes in Hoffman-Week's plot the modified SPBU samples indicated that T-m1 and T-m2 were originated from lamellar crystal and fringed micelle, respectively.