Polystyrene sheets are a common sight in many different environments. From protective packaging for in-home deliveries of more delicate items to hygienic packaging for fast food or insulation on construction sites. The paper investigates the mechanical properties of reinforced polystyrene by fibreglass, epoxy, and hardener. Three samples were developed and differ in the number of fibre layers used on both sides of polystyrene (1 layer, 2 layers, and 3 layers). Compression, impact, weight, and bending tests were performed on all samples following ASTM D3574, ASTM D6110, and ASTM E290 standards. The results show that the material weight gradually increased from 120 to 324 grams as three layers were added. Compressive strength increased by 33% from one layer on both sides to two layers and by 23,82% with three layers. The modulus of elasticity of the material increased by 39,55 % from one layer to two layers. The energy absorption increases by 50% from one layer of fibreglass on both sides to the second layer of fibre and by 40% from two layers on both sides to the third layer. The maximum bending stress decreased by 14.47% when the second layer of fibreglass was added to reinforce the material on both surfaces, and it decreased to 15.81% when the third layer of fibreglass and matrix was applied.