Narrowly-dispersed fluorescent octahedron and rounded-octahedron coordination polymer particles (CPPs) have been synthesized from the solvothermal reaction of In(NO3)3·xH2O and 2,6-bis[(4-carboxyanilino)carbonyl]pyridine. The shape and size of the resulting CPPs were dependent on the amount of solvent (and thus the concentration of reactants) used in the reaction. Under poor solubility conditions with only a small amount of DMF, the formation of coordination polymers proceeds quickly and the particle growth commences at a large number of sites, thus resulting in smaller particles. By decreasing the amount of DMF used in the reaction from 800 μL to 400 and 200 μL, the average size of the resulting CPPs was reduced from 2.22 ± 0.40 μm to 834 ± 120 and 431 ± 36.9 nm, respectively. In addition, we have found that some additives such as bipyridine and acetic acid, even though they were not incorporated within CPPs, did play an important role in the formation of CPPs by means of manipulating the deprotonation rate of organic building blocks and so affect the size and morphology of the resulting CPPs. Fluorescent octahedron and rounded-octahedron CPPs with specific size ranging from 307 nm to 2.22 μm were successfully prepared. Control of the size and morphology of colloidal particles is one of our central aims, both in terms of fundamental interest and for practical applications. Therefore, this work should provide significant assistance in the development of CPP materials.