In this paper, copper octacarboxyphthalocyanine (CuPc) was demonstrated to be an efficient photosensitizer of graphitic carbon nitride (g-CN) for the degradation of dyes like Orange II or Methylene Blue under visible light irradiation. UV-vis absorption, photoluminescence and photocurrent measurements demonstrate that CuPc not only allows to extend the absorption to wavelengths up to 1000 nm but also enhances the charge-transfer efficiency. The high photocatalytic efficiency of CuPc/g-CN nanohybrids originates from the strong association between the carboxylic acid groups of CuPc with g-CN which favor the transfer of photo-excited electrons from CuPc to g-CN. The CuPc/g-CN catalyst is stable, can be reused up to five times without significant loss of activity and is therefore of high potential for photocatalytic applications like wastewater treatment or hydrogen production under visible or near-infrared irradiation.