Polymeric dielectric materials show great values in various modern electronic devices. However, breaking the paradox between dielectric constant (εr) and breakdown strength (Eb) is still a great challenge for achieving the dielectric composites with high energy storage. In this paper, ultrasmall molybdenum disulfide (MoS2) nanodots with a size of ∼5 nm are prepared by gradient centrifugation, and the effect of nanodots on dielectric response is investigated via a comparative study with MoS2 nanoflakes. It is demonstrated that, both MoS2 nanodots and nanoflakes can induce poly (vinylidene fluoride) (PVDF) to generate more polar β-phases. Moreover, within composites, the presence of MoS2 nanodots contributes to a greater degree of freedom for the polymer molecular chains at interface, which is responsible for the low loss. In addition, the unique quantum effect of nanodots brings higher Eb to the composites, finally realizing the promotion of εr and Eb simultaneously. However, due to the relatively compact interface between the MoS2 nanoflakes and the polymer molecular chains, the molecular chains are harder able to respond to changes in the electric field, resulting in a limited εr and an unsatisfactory dielectric loss (tanδ). Among them, the composite filled with 0.05 wt% MoS2 nanodots achieves a highest discharge energy density (Ud) of 5.4 J/cm3, lowest tanδ of 0.015@103 Hz and the most considerable Eb of 510 MV/m. This work provides theoretical guidance for the preparation of high-performance dielectric composites.