High-electrocatalytic-activity noble nanoparticles (NPs) supported on carbon nanoballs (CNBs) were synthesized using an innovative plasma-in-liquid method, which is known as solution plasma processing (SPP). This technique uses a one-step method for the synthesis of NPs on carbon materials. CNBs are formed using benzene as a carbon precursor while gold (Au) or platinum (Pt) nanoparticles are generated instantaneously via sputtering from metal electrodes. The synthesized NP/CNBs were annealed at 850 °C in order to increase the conductivity of the material. The results of structural characterizations reveal that the Au and Pt NPs are smaller than 10 nm and have a uniform size distribution, and these NPs are successfully loaded onto highly mesoporous CNBs that have an average pore diameter between 13 and 16 nm. In the results from cyclic voltammetry measurements, the Au/CNBs and Pt/CNBs show clear peaks corresponding to the oxidation and reduction features in the catalytic reactions. Apart from noble nanoparticles, SPP can also be used to synthesize various kinds of NPs including bimetallic NPs loaded on spherical carbon supports by changing the working electrodes. The proposed mechanism for the synthesis is discussed in detail. This method shows potential to be a candidate for the next-generation synthesis of NP/carbon in the future.