Developing a reliable technique to organize nanoscale building blocks into ordered one-dimensional assemblies is of particular interest in a range of practical applications. Here, for the first time, it is reported that platinum (Pt) nanoparticle chain networks can be assembled spontaneously in solution on a large scale. The in-situ induced magnetic dipoles are believed to be the driving force for producing such elegant assembled nanochains. The alterant electronic structure of Pt modified by a very thin layer of polyvinylpyrrolidone (PVP) molecules leads to the ferromagnetism of Pt (a traditional paramagnetic metal), which has been verified by a series of analysis techniques and theoretical modeling. The temperature- and time-dependent nucleation, growth, and organization processes of Pt chain networks are carefully investigated. These findings not only present the uncommon ferromagnetism of Pt, but also raise a possibility for expanding this strategy towards other assemblies of nonmagnetic nanoscale building blocks.