In order to overcome the challenge of synchronously strengthening and toughening polypropylene (PP) with a low-cost and environmental technology, CaCO3 (CC) nanoparticles are modified by tartaric acid (TA), a kind of food-grade complexing agent, and used as nanofillers for the first time. The evaluation of mechanical performance showed that, with 20 wt.% TA-modified CC (TAMCC), the impact toughness and tensile strength of TAMCC/PP were 120% and 14% more than those of neat PP, respectively. Even with 50 wt.% TAMCC, the impact toughness and tensile strength of TAMCC/PP were still superior to those of neat PP, which is attributable to the improved compatibility and dispersion of TAMCC in a PP matrix, and the better fluidity of TAMCC/PP nanocomposite. The strengthening and toughening mechanism of TAMCC for PP involves interfacial debonding between nanofillers and PP, and the decreased crystallinity of PP, but without the formation of β-PP. This article presents a new applicable method to modify CC inorganic fillers with a green modifier and promote their dispersion in PP. The obtained PP nanocomposite simultaneously achieved enhanced mechanical strength and impact toughness even with high content of nanofillers, highlighting bright perspective in high-performance, economical, and eco-friendly polymer-inorganic nanocomposites.