Slightly oxidized graphene nanoplatelets (GNPs) were functionalized using 3-hydroxytyramine hydrobromide. The functionalized GNPs, denoted as fGNPs, were examined using Fourier transform infrared and a Raman spectrometer, which revealed a slight reduction in the sp2 network domain compared with unmodified GNPs. Compared with previous reports on functionalized highly oxidized graphene, the degree of the sp2 structural destruction was less, as revealed by Raman analysis. The aim was to address the challenges of high agglomeration of graphene in polymer matrix and high destruction of graphene’s conjugal structure during functionalization, which deteriorates graphene’s excellent properties and makes it less effective in improving the polymer’s properties. This was achieved by slight functionalization of GNPs because they contained little oxygen functional groups. In this study, a thermal conductivity increase of about 295 % was recorded when 6.67 wt. % fGNPs were incorporated into the poly(vinylidene fluoride) (PVDF) matrix. Also, with 3.34 wt. % of the GNPs composite, the tensile strength and Young’s modulus were measured with an increase of about 64 % and 100 %, respectively. The enhanced properties of the polymer nanocomposites were due to better dispersion of fGNPs and interaction with the polymer matrix compared to unfunctionalized GNPs composites as was indicated by a scanning electron microscope. The composites were prepared by solution blending and melt compounding process. Such composites can find application in automobile and aerospace industries in which good mechanical and thermal properties are required.