In order to develop water-soluble porphyrins, alkyloxo-(methoxo)porphyrinatoantimony bromides (alkyl = decyl, dodecyl, and octadecyl) were prepared. These complexes have more than 200 mg/100 g of solubility in aqueous Solution. From the analysis of absorption spectra and surface tension, it was elucidated that the porphyrin complexes are present as aggregates in aqueous solution.