This research has been conducted to investigate the effect of adding waste plastic fibers (WPF) in concrete on behavior of composites steel plate-concrete slabs. The WPF were produced by cutting plastic bottles used to preserve carbonated beverages. Both mid-span deflection and slip between concrete layer and steel plate are measured using an electronic gauge at 7, 28, 56, 90, 120, 180 and 270 day age. Percentages calculations of plastic fiber by volumetric rates ranging between (0 %) to (1 %) were carried out. Reference concrete slab without plastic fibers was cast for comparison. Short-term test was conducted on the slabs to determine the ultimate load. The tests results showed that 1 % WPF has led to lower value of deflection and highest slip between steel plate and slab concrete. There is a slight difference between the results of 0.75 % and 1 %WPF.