Attention to lightness in modern construction and the need to produce and use lightweight concrete in tall buildings has also led researchers to use lightweight synthetic materials. The aim of the research is to replace natural sand with 0-4 mm LECA sand in the production of lightweight structural concrete. Therefore, four mix designs were made with LECA sand and water-to-cement ratios of 600 and 0.42 kg/m3 in the first and third designs, and 200 and 0.35 kg/m3 in the second and fourth designs. After determining the compressive strength of the samples, the fourth mix design was determined as the reference design. Next, three new mix designs were made with 10%, 20%, and 30% replacements of polyethylene terephthalate aggregates and LECA sand. Standard cubic and cylindrical samples were prepared to determine the compressive strength and static modulus of elasticity, respectively, and were cured in water for 28 days. For all mix designs, slump and specific gravity tests were performed in the fresh and hardened states of the concrete. The results showed that the design with 10% polyethylene terephthalate replacement with LECA sand achieved an increase in compressive strength and static modulus of elasticity of 18.4% and 6.1%, respectively, compared to the reference mix design. The results showed that it is possible to use polyethylene terephthalate aggregates to produce structural lightweight concrete, even in such a way that this type of concrete has superior mechanical properties compared to the reference concrete.