Graphitic carbon nitride (C3N4) was hybridized by Bi2WO6 via a hydrothermal method. The high-resolution transmission electron microscopy (HR-TEM) results reveal that an intimate interface between C3N4 and Bi2WO6 forms in the heterojunctions. The UV-vis diffuse reflection spectra show that the resulting C3N4-Bi2WO6 heterojunctions possess more intensive absorption within the visible light range in comparison with pure Bi2WO6. These excellent structural and spectral properties endowed the C3N4-Bi2WO6 heterojunctions with enhanced photocatalytic activities. Significantly, the optimum photocatalytic activity of the 0.5C3N4-0.5Bi2WO6 heterojunction for the degradation of methyl orange (MO) was almost 3 and 155 times higher than those of either individual C3N4 or Bi2WO6. The possible photocatalytic mechanism with superoxide radical species as the main active species in photocatalysis is proposed on the basis of experimental results. Moreover, the heterojunction depicted high stability and durability during six successive cycles.