In this study, a novel nanodiamoands (NDs)/zinc (Zn) nanocomposite have been investigated as counter electrode (CE) in flexible dye sensitized solar cell (DSSC) device as potential replacement for platinum (Pt). Simple drop casting method has been employed to fabricate CE on indium tin oxide (ITO) coated Polyethylene terephthalate (PET) substrate. Various concentrations of Zn in optimized NDs layer have been investigated. Scanning electron microscopy (SEM) and X-Ray diffraction (XRD) methods have been utilized to study surface morphology and structural composition. Uv-vis has been employed to study light absorption characteristics. Fourier Transform Infrared (FTIR) has been used to identify redox active functionalities. Electron Impedance Spectroscopy (EIS) and Cyclic Voltametery (CV) have been employed to study electron transfer and catalytic activity and finally I-V testing has been conducted using sun simulator. The optimized layer of NDs displayed 78.52% equivalent performance compared to Pt based CE at optimum layer thickness. The introduction of Zn nanoparticles further improved the catalytic activity comparable or even exceeds the performance of Pt based reference CE. A 6.23% increase in performance has been observed at 8% Zn concentration compared to Pt based reference device. Further increment in concentration leads to reduction in performance due to charge trapping sites and agglomeration of nanoparticles.