Highly isotactic poly(2-vinylpyridine) (P2VP) was synthesized by the group transfer polymerization of the prochiral 2-vinylpyridine (2VP) with 2-methoxyethylamino-bis(phenolate)yttrium complexes. Isotacticities of up to P-m = 0.92, narrow molecular weight distributions, and high molecular weights were achieved by steric modifications of the variable bisphenolate ligand structure. The resulting polymer samples were characterized by thermoanalysis (DSC, TGA), GPC, and C-13 NMR. The origin of the isotactic microstructure was attributed to an enantiomorphic site control mechanism based on C-13 NMR mechanistic studies and allowed new insights into C-13 pentad assignments.