Here, a facile and green approach based on the coordinated electrodeposition of carboxymethyl cellulose (CMC) is developed to fabricate silver nanoclusters (AgNCs) and AgNCs/CMC nanocomposite films. In the approach, CMC not only serves as the electrodeposition polysaccharide, but also acts as the stabilizing agent and reducing agent for the synthesis of AgNCs, as well as the major component in the resulting AgNCs/CMC nanocomposite film. After the electrodeposition and incubation, a homogeneous and smooth film is generated on the anodic electrode, which exhibits a clear yellow florescence. Transmission electron microscopy observation shows that there are nanoparticles with the average size of 1.7 nm in the nanocomposite film. X‐ray photoelectron spectroscopy, UV–vis absorption spectroscopy, and fluorescence spectroscopy both confirm that there are AgNCs in the nanocomposite film. The AgNCs/CMC nanocomposite film shows the capability for fluorescence detection by using the fluorescence quenching features of AgNCs. Moreover, the AgNCs/CMC‐modified electrode can be conveniently and directly produced, which presents potential applications for electrochemical biosensors. Thus, this study provides a novel approach for the green synthesis of AgNCs and direct fabrication of the AgNCs/CMC nanocomposite film, which can be promisingly applied for constructing functional nanocomposites and advanced biodevices.