Objectives: This study evaluated the effect of incorporating Graphene oxide nanoparticles on the post-gel shrinkage strain and degree of conversion of resin composite restorative material. Materials and methods: Graphene oxide nanoparticles was synthetized and incorporated within a nanohybrid resin composite (Filtek™ Z250 XT). 20 specimens (7x4x2 mm) were fabricated for polymerization shrinkage and divided into 2 equal halves. 10 specimens were fabricated without incorporation with Graphene oxide nanoparticles (the control group; group 1), while the other half was incorporated with 2% concentration by weight and referred to group 2. The post-gel shrinkage strain was measured by strain gauge technique. The degree of conversion was measured using a Fourier Transform Infrared (FTIR) spectrometer. Similar groups specimens were prepared by polymerizing the material in a disc-shaped split white Teflon mold 2 mm thick and 4 mm in diameter. Ten disc-shaped specimens were prepared for each experimental condition. The resultant data were subjected to independent T-test (P≤0.05) to reveal the statistically significant difference. Results: The incorporation of Graphene oxide nanoparticles significantly reduced the post-gel shrinkage strain. On the other hand, the degree of conversion reported no significant difference between the two groups. Conclusion: Addition of Graphene oxide nanoparticles to resin composite restorative material positively affect the polymerization shrinkage while maintaining the degree of conversion.