Gold nanoparticles (AuNPs) were synthesized using allyl mercaptan (C3H6S) as the capping agent. It was expected that high affinity of gold to groups containing S as well as double bonds in allyl mercaptan structure can be used to form covalent bonds between AuNPs onto the BDD surface. The characterization of AuNPs using a UV-Visible Spectrophotometer produced specific wavelengths of gold nanoparticles in the range of 510-580 nm, while characterization using Transmission Electron Microscopy (TEM) and Particle Size Analyzer (PSA) showed an average size of AuNPs at 29 ± 5 The synthesized AuNPs were deposited on the surface of the BDD electrodes by immersion method under UV light (λ = 254 nm) and characterized using X-Ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS). Examination of arsenic sensor was carried out using the Anodic Stripping Voltammetry (ASV) technique. Measurements of As3+ using AuNPs-modified BDD (AuNPs-BDD) electrode showed current responses with good linearity (R2 = 0.99) in the concentration range 0-100 μM with limit detection values of As3+ of 0.064 μM.