Abstract: Wellbore instability is the main challenge encountered during borehole construction, particularly when employing water-based drilling fluid (WBDF) under complex geological conditions. A novel wellbore strengthening material of acrylic resin enhanced by hydrophobically modified calcium carbonate particles (ARH) is synthesized by emulsion polymerization. Transmission electron microscope and particle size analysis reveal that ARH exhibits a spherical structure with a Z-average diameter of 277.6 nm. The lap shear strength test shows ARH effectively adheres to two rock slices with a stress of 0.4838 MPa. Uniaxial compressive strength experiments of simulated rock cores verify that ARH can greatly enhance the compressive strength of the simulated core column to 7.1567 MPa. The incorporation of ARH significantly enhances the compressive strength of shale cores, with increases of 18.0620 and 18.9147 MPa compared to those immersed in water and base fluid, respectively. Further microporous membrane plugging experiments show that the filtration losses of 2% ARH in 4% base fluid through 0.1, 0.2, and 0.45 μm microporous membranes are 13.5, 13.2, and 27 mL, respectively, demonstrating excellent plugging capabilities for enhancing wellbore stability. This work generates important theoretical foundations and practical recommendations for wellbore strengthening applications utilizing ARH in complex drilling environments.