Nickel ferrite (NiFe2O4) and magnetite (Fe3O4) are established earth-abundant materials and get tremendous attention because of magnetic and high photocatalytic activity. First we fabricated novel Fe3O4@20 wt % NiFe2O4/phosphorus-doped g-C3N4 (M@NFOPCN) using a convenient simple coprecipitation method followed by calcination at 400 °C. Then M@NFOPCN composites were prepared by the in situ growth of Fe3O4 nanorods and cubes on the surfaces of a porous agglomerated NFOPCN nanostructure, varying the weight percentage of Fe3O4. A series of characterizations like X-ray diffraction, UV-vis diffuse-reflectance spectroscopy, photoluminescence, Fourier transform infrared, thermogravimetric analysis-differential thermal analysis, vibrating-sample magnetometry, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy techniques confirm that changing weight percentage of M can constructively control the textural characteristics, internal strain, size of the crystals, and other aspects meant for photocatalytic activity. When M was coupled with NFOPCN, magnetic loss was lowered and also an appreciable saturation magnetization (Ms) was obtained. 40 wt % M@NFOPCN showed admirable photostability and was capable of evolving 924 μmol h-1 H2 when irradiated under visible light. The percentage of degradation for ciprofloxacin (CIP) by this ternary nanocomposite was almost 2-fold greater than those of the pure M and NFOPCN photocatalysts. A plausible photocatalytic mechanism for the degradation of CIP antibiotic was established. Hence, this study presents a reusable, low-cost, noble-metal-free, environmentally friendly, fast, and highly efficient 40 wt % M@NFOPCN photocatalyst, achieving 90% degradation of CIP antibiotic under visible light. The double-Z scheme triggers charge separation and migration, enhances visible-light harvesting, and helps in internal electric-field creation, thus headed toward dramatic augmentation of the photocatalytic activity.