Self‐assembly of nanomaterials, directed by molecular or supramolecular interactions, is a powerful strategy to build nanoscale devices. Despite many advantages of such solution‐based processes, a big challenge is to realize interparticle ohmic contacts toward facilitated charge transport over a long distance. We report a new concept of primed nanowelding to thread solution‐borne nanoparticles in prescribed assemblies. The process starts with a gap‐specific deposition of Ag2E (E=S, Se) materials in pre‐assembled gold structures, which spontaneously transform into AgAuE semiconductors via directional gold diffusion. Treatment with tributylphosphine generates alloyed Au/Ag welding spots that conductively wire‐up nanoparticles into discrete "molecules" and micron‐long "polymers". This method is compatible with DNA programming and delivers a possible way to solve the problem of the carrier‐transport dilemma in solution‐processed nanostructures for better‐functioning nanodevices. [ABSTRACT FROM AUTHOR]