The incorporation of cobalt, nickel, copper, and oxovanadium(IV) into nonpolar 5,10,15,20-tetraphenyl-21H,23H-porphyrin (H2TPP) occurred with their sulfates, nitrates, and chlorides in high-temperature water. The yield of metalloporphyrin significantly increased with increasing temperature for cobalt, nickel, and copper sulfates from 473 to 673 K, which means that the high temperature region was preferred for the incorporation of metals into the porphyrin structure. In high-temperature water, most of H2TPP dissolved, whereas almost all of metals probably existed in solid phase. The incorporation of metal into a porphyrin structure was almost first-order with respect to H2TPP and probably proceeded through the pre-equilibrium state between metal ion and H2TPP.