The increasing accumulation of plastic waste has led to environmental concerns, prompting researchers to explore sustainable methods for its utilization in construction materials. This study investigates the impact of PET plastic waste replacement on the water absorption and compressive strength of cement and soil bricks. PET plastic was incorporated at replacement levels of 5%, 10%, 15%, and 20% in cement bricks, and at 5% and 10% in soil bricks. The results indicate that water absorption in cement bricks increases with higher PET content, reaching 10.95% at 20% replacement due to increased void formation. In contrast, soil bricks exhibit a reduction in water absorption, dropping from 13.73% at 5% PET to 11.09% at 10%, as plastic particles fill the pores. Compressive strength testing revealed that cement bricks achieve a peak strength of 7.68 MPa at 5% PET replacement, followed by a decline with further plastic addition. Soil bricks, however, showed a consistent decrease in strength, from 3.41 MPa at 5% PET to 2.34 MPa at 10% the strength. Therefore, the results satisfy the minimum compressive strength requirement specified in IS 1077:1992 for common burnt clay bricks. The findings also suggest that PET incorporation can enhance cement brick strength at lower replacement levels while reducing water absorption in soil bricks. This study highlights the potential for PET waste utilization in sustainable construction, with careful optimization required to balance strength and durability.