Triangular silver nanocrystals, well-known as nanoprisms (Ag-NPrs), were successfully developed via a robust and straightforward direct chemical reduction synthetic approach, producing desirable tiny and well-controlled Ag-NPrs. This procedure was accomplished by fabricating a mixture of di-sodium succinate hexa-hydrate (DSSH) and tri-sodium citrate di-hydrate (TSCD) as capping agents at optimal synthetic conditions and under an open-air condition, which proved to be an enormous challenge. Additionally, the Ag-NPrs were fully characterized by UV-vis spectra, X-ray diffraction (XRD), scanning electron microscope (SEM), and dynamic light scattering (DLS). Likewise, the formation stages from spherical silver nanoparticles (Ag-NPs) to triangular Ag-NPrs were also captured simultaneously via transmission electron microscope (TEM) and high-resolution transmission electron microscope (HR-TEM) images. More interestingly, an active thin silica-shell was efficiently applied on the Ag-NPrs outer-layer to increase their functionality. Furthermore, to confirm their biocompatibility, we also carried out cell viability assays for the Ag-NPs, Ag-NPrs, and Ag-NPrs@SiO2 with different concentrations at 62.5, 125, and 250 µg/mL after 12, 24, and 48 h of exposure time, respectively, on a regular African green monkey kidney cell line. The cell viability test results exemplified that the three silver nanostructures were toxic-free and suitable for further potential biological applications in the near future.