A facile solution-based method to synthesize cobalt nanofibers with a complex pine-tree-leaf like architecture has been developed. Mechanistic formation processes of this synthetic approach have been revealed, and some important preparative parameters related to the synthesis have been identified and investigated with some designed experiments. In view of the presence of hierarchical organization, ferromagnetic properties of the cobalt nanofibers have been further differentiated for the different structural parts within the complex fiber architecture. A process for making metallic disks or papers has been devised. These lightweight cobalt materials are magnetically responsive, exhibiting an extraordinary ultrahydrophobicity (water contact angle 172.3°). Owing to their unique structural features and other physicochemical properties, the cobalt nanofibers have good potential for use in future applications.