Polymorphic nucleation of carbamazepine (CBZ) in several solvents (ethanol, 2-propanol, acetone, acetonitrile, toluene, and nitromethane) was investigated with different functionalized porous silica templates. It was found that the introduction of silica templates with different surface chemistries such as −OH, −NH2, and −phenyl affected the polymorphic outcomes. At a low supersaturation ratio, stable form III of CBZ was prone to nucleate as expected. However, the results in this work confirmed that a phenyl-functionalized porous silica template could crystallize and maintain metastable form II of CBZ at a low supersaturation ratio for a long time. In terms of the underlying mechanism, the aromatic–aromatic interaction between the surface of phenyl-functionalized silica and the CBZ molecule played an important role in stabilizing metastable form II. The influence of the amount of silica templates on the polymorph formation was also investigated. Our results will help to crystallize and maintain metastable materials, even at a low supersaturation ratio.