Jute fiber (Hessian cloth) and E-glass fiber (mat)-reinforced, unsaturated polyester (USP) resin along with additives and initiator, composites are prepared by the hand layup technique at room temperature (25°C). Jute fiber content in the composites is optimized with the extent of mechanical properties, and composites with 25% jute show higher mechanical properties. The mechanical properties are found to increase with the incorporation of dissimilar portions of glass fiber into the jute fiber-reinforced composite. Among all the resulting hybrid composites, the composite with a jute to glass ratio of 1: 3 demonstrates improved mechanical properties, such as tensile strength (TS) 125%, tensile modulus (TM) 49%, bending strength (BS) 162%, and bending modulus (BM) 235% over untreated jute composite. To further improve the properties, the surface of jute and glass fiber is irradiated under UV radiation of different intensities. UV pretreated jute and glass fibers (1: 3) at optimum intensities show the highest mechanical properties, such as TS 70%, TM 33%, BS 40%, and BM 43% compared to untreated jute-and glass-based hybrid composites. UV-modified jute/glass-reinforced hybrid composites also show the best of Charpy impact strength (40 kJ/m²). The interfacial adhesion between jute/glass and USP is monitored by a scanning electronic microscope (SEM).