A composite film of PEDOT:PSS/TiN-NPs, containing poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and titanium nitride nanoparticles (TiN-NPs), was deposited on a Ti foil by a doctor blade technique. Various weight percentages of TiN-NPs (5, 10, 20, 30 wt%) were used to prepare different composite films. This Ti foil with the composite film was used as the flexible counter-electrode (CE) for a dye-sensitized solar cell (DSSC). Performances of the DSSCs with the platinum-free CEs containing PEDOT:PSS/TiN-NPs with various contents of TiN-NPs were investigated. After the optimization of composition and thickness of the composite film PEDOT:PSS/TiN-NPs, a light-to-electricity conversion efficiency (η) of 6.67% was achieved for the pertinent DSSC, using our synthesized CYC-B1 dye, which was found to be higher than that of a cell with a sputtered-Pt film on its CE (6.57%). The homogeneous nature of the composite film PEDOT:PSS/TiN-NPs, the uniform distribution of TiN-NPs in its polymer matrix, and the large electrochemical surface area of the composite film are seen to be the factors for the best performance of the pertinent DSSC. Scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy dispersive X-ray spectroscopy (EDX) were used to characterize the films. The high efficiency of the cell with PEDOT:PSS/TiN-NPs is explained by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and incident photon-to-current conversion efficiency (IPCE) curves.