Highly sensitive detection of a Pb2+-Cu2+ mixture using gold nanoparticles patterned on single-walled carbon nanotube (AuNP-SWCNT) film is reported. The gold nanoparticles were deposited electrochemically on carbon nanotube film using a cyclic voltammetry technique. The film showed a homogeneous size and density that could be easily controlled by the potential scanning cycle and gold precursor concentration. Square wave stripping voltammetry (SWSV) was applied to the simultaneous detection of Pb2+ and Cu2+ under optimized conditions. The AuNP-SWCNT electrode exhibited a high increase in sensitivity with a limit of detection of 0.546 ppb (R2 = 0.984) and 0.613 ppb (R2 = 0.991) for Pb 2+ and Cu2+ ions, respectively, in a mixture of Pb 2+-Cu2+ solution (S/N = 3, n = 5), and a good linear response in the range from 3.31 ppb to 22.29 ppb. The electrode exhibited high reproducibility in repetitive measurements with a relative standard deviation as low as 4.2% and 2.6% for Pb2+ and Cu2+ ions, respectively. An interference study showed that Sb3+, As 3+, Zn2+, Ca2+, and Na+ ions did not have a significant effect. This study demonstrated an alternative approach to the rapid and reliable detection of heavy metals of environmental interest.