Herein,　a　simple　and　feasible　electrochemical　immunosensing　method　for　simultaneous　voltammetric　detection　of　two　immunoglobulin　proteins,　human　IgG　(HIgG)　and　rabbit　IgG　(RIgG),　was　developed　using　two　distinguishable　signal-generation　tags　on　the　same　electrode.　The　immunosensor　was　prepared　by　immobilizing　two　Fab　antibody　fragments　on　a　gold　electrode.　After　this,　Cu　and　Cd　nanocrystals,　as　nanotags,　were　synthesized　and　functionalized　with　identical　detection　antibodies.　Transmission　electron　microscopy　(TEM)　and　Fourier　transform　infrared　spectroscopy　(FTIR)　were　employed　to　characterize　the　Cu　and　Cd　nanocrystals.　The　covalently　modified　electrode　with　the　Fab　antibody　fragments　through　the　Au-Thiolate　bond　(to　dispel　the　non-specific　adsorption)　was　investigated　via　scanning　electron　microscopy　(SEM).　After　the　sandwiched　immunoreaction,　the　antibody-modified　nanocrystals　were　captured　on　the　immunosensor,　which　could　be　interrogated　in　pH　3.5　HCl　using　square-wave　anodic　stripping　voltammetry.　Experimental　results　also　indicated　that　the　multiplexed　immunoassay　enabled　the　simultaneous　detection　of　HIgG　and　RIgG　in　a　single　run　with　the　similar　linear　range　from　0.01　to　10　ng　mL-1,　and　the　limits　of　detection　(LODs)　towards　two　analytes　could　be　as　low　as　3.4　pg　mL-1　(at　3σ).　Acceptable　assay　results　on　precision,　reproducibility,　specificity,　and　method　accuracy　were　also　acquired.　Importantly,　the　newly　designed　strategy　avoided　cross-Talk　and　enzymatic　introduction　as　compared　to　conventional　electrochemical　immunoassays,　thus　exhibiting　a　promising　potential　in　clinical　applications.　©　This　journal　is　The　Royal　Society　of　Chemistry.