This paper presents the influence of polyolefin fiber on the flexural and shear attitude on the flat slabs. Three slab sets (80 cm × 80 cm) were tested, each with a thickness of 10 cm. In the first set (S1), the effect of fiber content on the flexural behavior of the flat slab was considered. Therefore, four slab specimens were cast, one of which was considered as a control specimen with no fiber content, while the other three included fibers at 0.5, 1, and 1.5 percent of the total concrete volume. The second series of experiments studied the flexural behavior of flat slabs (S2) with an opening of 15 cm × 15 cm. The first specimen contained nil polyolefin, while the second included 1% polyolefin. In the third set (S3), consideration was taken for 0 and 1% of Polyolefin to realize the shear behavior of the flat slab. The increase in polyolefin fiber content from 0 to 1.5% (for slab set 1) will decrease the deflection from 4.5 mm to 2.3 mm, with an average of 3.58 mm, which is close to the deflection of a 1% polyolefin fiber specimen. Three dimensional models for the tested slabs were simulated numerically via ABAQUS software program. The ratio of the maximum deflection between the experimental and the numerical outcomes were varied with a range of 1.01 to 1.28, with an average of 1.14.