Disulfide-rich animal venom peptides that inhibit voltage-gated sodium channel 1.7 (Na_V1.7) have been widely studied as drug leads for the treatment of chronic pain. Recently, native peptide toxins containing two distinct homologous binding domains have been discovered which exhibit superior potency and channel affinity compared to their monovalent constituents. In this study, the pore-blocking cone snail-derived μ-conotoxin KIIIA is enzymatically ligated to the spider-derived gating modifier toxin PaurTx3 using sortase A. The bivalent peptide was optimized by varying the order of the toxins and length of the linker between them, and its pharmacological properties were evaluated using electrophysiology and human serum stability assays. We determined an ideal linker length which allowed both peptide domains to reach their respective binding sites, creating a stable synthetic heterodimeric peptide with greater potency and channel affinity at Na_V1.7 than either of the peptides individually. This work shows that novel Na_V1.7 inhibitors can be designed from a pore blocker and a gating modifier to confer desired pharmacological properties from both domains.