Statement of Problem: Polymerization shrinkage is one of the major problems of the current dental composites and it can cause marginal gap and post-operative sensitivity.Purpose: The purpose of this study was to investigate the effect of nanoporous fillers on the polymerization shrinkage and degree of conversion of an experimental dental composite in three different curing modes and also comparing its results with another experimental composite containing conventional fillers.Methods and Material: In this study, the experimental composite was prepared by mixing the silane treated fillers with monomers. The monomers consisted of 70% Bis-GMA and 30% TEG DMA by weight. The experimental composite was divided into two groups according to their filler type, i.e. conventional micro-hybrid and nanoporous. In order to make nanoporous fillers, the fillers were sintered in 1300°c and grinded Camphorquinon and DMA EMA were used as initiator-accelerator systems. Polymerization shrinkage was measured using bonded disc method in three curing modes (High Intensity, Ramp, Standard). The degree of convention was measured using FTIR spectroscopy.Result: The results showed that the nanoporous fillers have a positive effect on the reduction of polymerization shrinkage strain. No significant difference was found in polymerization shrinkage of the three curing modes. Neither the type of the fillers nor the mode of cure had an effect on the degree of conversion.Conclusion: Lower polymerization shrinkage strain can be achieved by using nanoporous fillers. The mode of cure does not affect the polymerization shrinkage.Key words: Nanoporous filler, Polymerization shrinkage, Degree of convention, Bonded disk method