Cobalt microspheres constructed by the assembly of nanoplatelets have been synthesized by awet chemical reductive procedure at room temperature with the help of glycerin and citric acid and without additional surfactants. The size of the microspheres is about 2–5 mand that of the nanoplatelets assembled the microspheres is tens of nanometers in thickness. In this synthetic system, cobalt acetate was employed as Co source, sodium hydroxide was used to manipulate the pH value of the reaction system, and hydrazine hydratewas used as a reducing agent. A series of experimentswere performed with different amounts of glycerin, from 0.5mL to 4 mL, the results reveal that the formation of cobalt microspheres is assisted by glycerin. The shape, structure, and magnetic properties of the final products were invstigated by XRD, SEM and VSM. This kind of Co nanostructures shows a ferromagnetic behavior at room temperature with enhanced coercivity, and has potential uses in magnetic recording devices and other related nanodevices. A possible mechanism for the formation of microspheres is proposed.