This paper presents an experimental study on the flexural behavior of encased flat cold formed steel sections FCFS and perforated cold formed steel sections PCFS. A full scale eleven specimens were prepared and tested till failure. One specimen without steel cold formed section tested as a control beam. Six specimens with flat steel cold formed section were tested to figure out the enhancement effect of section area and position. Finally, four specimens with a new shape of perforated steel cold formed sections were tested with different positions. Cold formed steel section height, flange width, and position are the main parameters studied and investigated. The ultimate load and vertical deflections were recorded and investigated. Also, modes of failure of the control and composite concrete beams were studied. From the experimental investigations, it has been observed that there is significant increase in ultimate load of composite beams with a perforated steel cold formed section. A significant increasing in the ultimate load was observed for specimens with perforated steel cold formed section.