Silver nanoparticles (AgNPs) were successfully synthesized via a rapid and convenient electrochemical method using sodium montmorillonite (MMT), a naturally occurring mineral, as both a stabilizer and a carrier. X-ray diffraction results showed that the AgNPs had face-centered cubic crystal structure. Inductively coupled plasma-atomic emission spectral analysis indicated that the AgNP yield increased with increasing the reduction potential. UV-vis absorption curves demonstrated that the AgNPs had optical absorbance at ca. 412 nm and showed a spectral blue-shift resulting from a decrease in the particle size. Transmission electron microscopy confirmed that after a centrifugation clarification process, the AgNPs formed in the aqueous solutions at reduction potentials of 5, 10, 15, and 20 V had average sizes of 4.2, 5.6, 15.3, and 20.5 nm, respectively. In contrast, in the as-prepared AgNP/MMT aqueous solutions, the AgNPs on the MMT surface had average sizes of 5.1, 8.0, 17.0, and 25.0 nm at reduction potentials of 5, 10, 15, and 20 V, respectively. Measurement of the inhibition area of antibacterial activity demonstrated that the AgNP/MMT nanocomposites had promising antibacterial applications.