Calcium carbonate nanoparticles were synthesized from eggshell waste using ball mill treatment and characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), and field-emission scanning electron microscopy (FESEM) analysis. Then, waste eggshell-derived nano calcium carbonate (WESNCC) was used as filler to reinforce natural rubber (NR) composites with and without the presence of maleated natural rubber (MNR) as compatibilizer. MNR-compatibilized NR/WESNCC composites showed remarkable enhancement in the torque difference, tensile, and thermal properties as compared to either uncompatibilized NR/WESNCC composites or unfilled NR system. Crosslinking degree measurements indicated excellent interfacial interaction between NR matrix and WESNCC in presence of MNR as compatibilizer. A probable mechanism is suggested to explain the interaction between NR matrix and WESNCC in the presence of MNR. This study provides unique way to develop WESNCC-based rubber composites for future industrial and engineering application. POLYM. ENG. SCI., 59:1428-1436 2019. (c) 2019 Society of Plastics Engineers