We synthesized silver nanoparticles (AgNPs) with a diameter ranging from 300 to 800 nm by chemical reduction, added them into commercial silver paste used for the front-contact metallization of crystalline Si (c-Si) solar cells, and investigated the effects of AgNPs on the firing behavior of the silver paste on c-Si solar cells by differential scanning calorimetry, electron scanning microscopy, and contact resistance measurement. It was observed that surface sintering of AgNPs occurred at a lower temperature compared with that of micrometer-sized Ag particles in commercial silver paste. With the assistance of AgNPs, more Ag⁺ ions were dissolved in fluidized glass frit during the firing process of the paste, and a continuous layer of Ag was reduced and deposited between glass frit and Si substrate. The Ag layer enhanced electrical conduction and decreased the specific contact resistivity of the paste on c-Si solar cells. Thus, a firing mechanism of AgNP-aided silver paste was proposed. The experimental data demonstrate that AgNPs can be used to improve the properties of the fired paste on c-Si solar cells and AgNP-aided silver paste is a promising material used for the front-contact grids on c-Si solar cells.