Ultra-fine fibril composites were produced by electrospinning of a polymer solution containing polystyrene (PS)/dimethylformamide (DMF) with different concentrations of three-dimensional graphite nanoplatelets (3D-GNPs). Berry's number of PS/DMF polymer solution was extensively studied to produce minimum electrospun PS fiber diameters. Three-dimensional GNPs of different weight percentages were dispersed in the optimized PS/DMF to produce ultrafine fibril composite fabric. The electrospun average diameters decreased from 1.5 μm for PS fibers to 890 nm for 3D-GNPs/PS fibril composites, respectively, at 12 and 9.8 Berry's number. High-resolution transmission electron microscopy samples' micrographs confirm a homogenous dispersion and alignment of 3D-GNPs in PS fibril composites. Thermal and mechanical characteristics of fabrics were determined using thermogravimetric analysis, thermomechanical Analysis, and dynamic mechanical analysis (DMA). It was found that there was an increase in percentage elongation, tensile strength, thermal stability, and glass-transition temperature for 3D-GNPs PS fibril composite fabrics compared to PS fabrics. Diminishing the value of loss tangent, measured by DMA, was used as an approach to predict the maximum amount of 3D-GNPs weight percent dispersion in electrospun PS/dimethylformamide solution. One of the most important potential applications of the electrospun 3D-GNPs/PS fibril composite fabrics is in the interiors of vehicles and aerospace industries as it characterizes by its good thermal and mechanical properties as well as its low density.