This investigation highlights different surface functionalization processes of Carbon Nano Fibres (CNF’s) and their effects on mechanical properties of Polyetherketone (PEK) nano composite. Surfaces of CNF’s were modified by low pressure plasma process. There is a significant change in physico-chemical characteristics of CNF’s after low plasma treatment as evident from Transmission Electron Microscopy (TEM) and Fourier Transform infrared Spectroscopic (FTIR)studies. Significant modification in surface morphology and oxygen functionalities are observed as a result of surface modification. There is a significant increase in mechanical properties of high performance polymeric nano composites when surface functionalizedCNF’s aredispersed inpolymeric matrix.