Composite films that consisted of C60 and well-exfoliated nanosheets of transition metal dichalcogenides (TMDs), such as MoS2 or WS2, with a bulk heterojunction structure were easily fabricated onto a semiconducting SnO2 electrode via a two-step methodology: self-assembly into their composite aggregates by injection of a poor solvent into a good solvent with the dispersion, and subsequent electrophoretic deposition. Upon photoexcitation, the composites on SnO2 exhibited enhanced transient conductivity in comparison with single components of TMDs or C60, which demonstrates that the bulk heterojunction nanostructure of TMD and C60 promoted the charge separation (CS). In addition, the decoration of the TMD nanosheets with C60 hindered the undesirable charge recombination (CR) between an electron in SnO2 and a hole in the TMD nanosheets. Owing to the accelerated CS and suppressed CR, photoelectrochemical devices based on the MoS2–C60 and WS2–C60 composites achieved remarkably improved incident photon-to-current efficiencies (IPCEs) as compared with the single-component films. Despite more suppressed CR in WS2–C60 than MoS2–C60, the IPCE value of the device with WS2–C60 was smaller than that with MoS2–C60 owing to its inhomogeneous film structure.