Introduction. The aim of this study was to determine the effect on the flexural strength of the self‐cured acrylic resin by incorporating short E‐glass fiber (SEGF) and ultra‐high‐molecular‐weight polyethylene (UHMW‐PE) filler in the acrylic resin. Methods. Fifty‐six rectangular (64 × 10 × 3.3 mm3) (ISO standard 20795–1:2013) self‐cured acrylic resin specimens were fabricated and divided into seven groups per test, according to the percent by weight of SEGF and UHMW‐PE filler (n = 8). Each testing group entails a control group and an addition of 1% and 2% SEGF, 1% and 2% UHMW‐PE, 0.5% SEGF/UHMW‐PE, and 1% SEGF/UHMW‐PE. A three‐point bending test was conducted to obtain the flexural strength of each specimen. The fractured surfaces of the specimens were evaluated, and a scanning electron microscope view was taken. Test results were statistically analyzed with one‐way ANOVA and Tukey HSD tests (p value<0.05). Results. The flexural strength of self‐cured acrylic resin with the addition of 1% SEGF and 1% SEGF/UHMW‐PE (50.93, 46.13 MPa) was significantly higher than that of the control group (41.72 MPa) (p < 0.05). Nonetheless, the addition of 1% UHMW‐PE (39.34 MPa) showed the lowest flexural strength, significantly lower than other experimental groups, except the control group. Conclusion. The addition of 1% SEGF significantly improves the flexural strength of the self‐cured acrylic resin denture base.