A polymer-sensitized g-C3N4/ZnFe2O4 photocatalyst was prepared by in situ calcinations followed by loading of PANI by physisorptions and in situ oxidative polymerization method. The synthesized nanocomposites were characterized by using XRD, FTIR, UV-vis DRS, XPS, PL, SEM and TEM analysis. A good coordination between CN, ZF and PANI was confirmed from FTIR as well as TEM images. The visible light active PANI-sensitized g-C3N4/ZnFe2O4 heterostructure was used for the photoreduction of Cr (VI) and the photooxidation of phenol simultaneously. However, the photocatalytic reduction of Cr (VI) occurs more rapidly for the coexistence system of phenol and Cr(VI) in comparison to single species, showing synergetic effect. Furthermore, it was found that PANI exhibits excellent photosensitization effect to enhance light absorption. The enhanced photo catalytic activity of PANI-sensitized g-C3N4/ZnFe2O4 photocatalyst is in good agreement with the obtained photocurrent results. PANI-sensitized g-C3N4/ZnFe2O4 photocatalyst gives an anodic photocurrent density of 2.5 mA/cm(2) and cathodic current of -1.6 mA/cm(2), which is much more than that of the neat counterparts. The first-order kinetic constant of photo catalytic Cr(VI) reduction in presence of phenol was 0.0324 min(-1), being about three times more than that for the reduction of single species chromium. The results obtained from this study illustrate that the prepared PANI-sensitized g-C3N4/ZnFe2O4 photocatalyst can be very well used as an effective and economically viable catalyst due to the ease of separation, and for simultaneous removal of toxic contaminants like Cr(VI) and phenol from wastewater. This magnetic based semiconductor photocatalyst is of great concern to overcome the problem of separation and secondary pollution. This method can also be highly desirable for environmental remediation due to the use of no additional scavengers in this process.