This research investigates the structural behavior of hybrid beams made with lightweight concrete (LWC) and engineering cementitious compounds (ECC). The study focuses on evaluating the flexural strength of LWC beams made with recycled plastic waste materials and reinforced with ECC-containing steel fibers. A total of eight solid and hollow reinforced concrete beams were meticulously fabricated and subjected to flexural loading. The main variables encompassed the strengthening region specifically, whether the strengthening occurred in the compression and tension regions, hollow core existence, and the thickness of the ECC layer. The findings revealed a notable increase in the ultimate flexural strength of LWC beams with the incorporation of ECC. Moreover, beams hybridized in both compression and tension regions exhibited a more pronounced enhancement in flexural strength compared to those hybridized in the compression region only. The LWC beam partially strengthened ECC layer in the compression zone showed an increase in first crack load, and ultimate load capacity with (9.5 and 19.65) % respectively. The presence of ECC in the tensile zone offered higher ultimate load capacity, as it contributed to delaying the propagation of the crack. Also, enhanced the first crack resistance, ultimate loads, and deflection with (90.47, 41.3, and 60.4) % respectively. Ductility, the energy absorption capacity, and initial stiffness of the hybrid beams in the compression and tension zone showed enhancement by (111.7, 179, and 62.45) % respectively.