Electrochemical analysis based on screen-printed electrodes (SPEs) represents a great alternative to conventional analytical methods such as ICP-MS or LC-MS, due to their portability, sensitivity, selectivity, and cost effectiveness. In addition, functionalization of SPEs with nanomaterials has been reported to provide an enhanced analytical performance [1,2]. In this regard, silver nanoparticles (AgNPs) were synthesized and appropriately characterized, showing spherical silver nanoseeds (Ag-NS) with a diameter of 12.20 ± 0.04 nm. Using spin coating methodology, the synthesized AgNPs were used to modify screen-printed carbon nanofiber electrodes (SPCNFEs). Ag-NS deposition onto the electrode surface was confirmed by scanning electron microscopy (SEM). Furthermore, the analytical response of the modified electrodes (Ag-NS-SPCNFE) was evaluated for the determination of trace lead(II), cadmium(II), and arsenic(V) using differential pulse anodic stripping voltammetry (DPASV), obtaining detection limits of 2.8, 2.1, and 0.6 µg·L^-1, respectively [3,4]. The results validated the hypothesis that Ag-NS modified electrodes presented higher sensitivity and better analytical performance than non-modified SPCNFE. Finally, the modified SPCNFEs were tested towards the determination of As(V) in a spiked tap water sample, showing a good agreement with concentrations determined by inductively coupled plasma-mass spectrometry (ICP-MS).