Objective: To investigate the reinforcing effect of short E-glass fibre fillers on fracture related mechanical properties of dental composite resin with a semi-interpenetrating polymer network (IPN) polymer matrix. Methods: Experimental short fibre composite (FC) resin was prepared by mixing 22.5 wt% of short E-glass fibres, 22.5 wt% of IPN-resin and 55 wt% of silane treated silica fillers using a high speed mixing machine. Test specimens were made bar shaped (3 × 6 × 25 mm3), cylindrical (6 mm length × 3 mm diameter) and cubic (9.5 × 5.5 × 3 mm3) from the experimental FC resin and conventional particulate composite resin (Grandio) as control. The test specimens (n = 8) were either dry stored or water stored (37°C for 30 days) before the mechanical tests. A three-point loading test and compression test were carried out according to ISO 10477 and a static loading test was carried out using a steel ball (Ø 3.0 mm) with a speed of 1.0 mm/min until fracture. Results: Experimental fibre composite had a significantly higher mechanical performance for fracture toughness (14 MNm-1.5), compression strength (129 MPa) and static load-bearing capacity (1584 N) than the control composite (2 MNm-1.5, 112 MPa and 1031 N). Conclusion: The resin with short E-glass fibre fillers and IPN-polymer matrix yielded improved mechanical performance compared to the conventional particulate composite resin. Schlagwörter: compression strength, fibre-reinforced composite, fracture toughness, restorative composite