Abstract The stereochemical configuration of poly(dialkyl fumarate)s (poly(DRF)) bearing t-butyl groups, i.e. poly(di-t-butyl fumarate) (poly(DtBF)) and poly(methyl t-butyl fumarate) (poly(MtBF)), was investigated by means of 13C nuclear magnetic resonance spectroscopy at 100 MHz. The microstructures of the polymers prepared by radical polymerization at 120°C were examined after they were transformed into poly(dimethyl fumarate) (poly(DMF)) by quantitative thermolysis and esterification in order to facilitate analysis of the spectra. The simulation of the spectra was carried out with the aid of modified Bernoullian statistics. It was revealed that the probability of meso addition in the propagation increased as a bulky ester group was introduced into DRF, i.e. in the order DtBF > MtBF > DMF. The average fraction of meso diads in poly(DtBF) increased when the polymerization temperature decreased.