Nanotechnology provides potential benefits for enhanced oil recovery (EOR) in low-permeability reservoirs. In this paper, SiO2/P(MBAAm-co-AM) composite nanoparticles were prepared using the distillation precipitation polymerization method. Scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis were employed to characterize the morphology and microstructure of nanoparticles. The swelling behavior of polymeric nanoparticles in brine was investigated to evaluate the effect of salinity and temperature. Kinetic and thermodynamic analyses were employed to reveal the swelling mechanism. Displacement experiments were performed to investigate their performance in EOR in low-permeability reservoirs. The results show that the swelling ratio of SiO2/P(MBAAm-co-AM) composite nanoparticles is higher at low salinity and high temperature, which can be explained by the Flory theory. The swelling process is spontaneous and endothermic, being controlled by physical adsorption involving the diffusion of water molecules, which complies with the first-order kinetics model. The suspension of SiO2/P(MBAAm-co-AM) composite nanoparticles can improve incremental oil recovery from 10.28 to 21.97% with an increase of the swelled particle size from 580 to 1160 nm. It is feasible that core-shell polymeric nanoparticles can be used for EOR in low-permeability reservoirs.