Implementing a flange opening in the existing beam makes cracks surrounded the opening due to stress concentration, reduces beam stiffness, and alters the simple beam behavior to a more complex one. This paper shows the behavior of reinforced HSC T-sections with flange opening un-strengthened by additional reinforcement in the bending zone. For this purpose, six HSC beams divided into two groups were cast and tested. The tested beams were supported and loaded under a point load effect in the middle of the beam span. The studied parameters were flange opening number (without, single, and double) and main reinforcement ratio (µ). Cracking and failure loads were recorded; deflections at the position of mid-span were measured. The pattern of cracks and modes of failure were observed. It was found that decreasing the compression zone width by flange openings and increasing the main reinforcement ratio significantly affected cracking and maximum loads, a pattern of cracks, and maximum induced deflections and strains, i.e., bearing capacity and deformation capacity of such tested beams