Abstract The use of waste and recycled materials in the construction industry, especially in concrete production, is becoming increasingly popular. The production of cotton underwear generates a certain amount of knitted fabric waste. This study was conducted to investigate the possibility of using cotton knitted fabric waste (CKFW) in concrete and to explore its potential application in the construction industry. The aim of the study is not only to reduce the waste but also to add positive properties to the concrete. A total of 4 mixes were prepared for testing purposes. CKFW were cut into small pieces of size about 6-8 cm x 2 cm. The addition of CKFW was a substitute for aggregates and replaced 0, 2.5, 5 and 10% of the total volume of aggregates in the concrete mix to make the concrete lighter. All mixes have the same amount of cement, water and superplasticizer. The knitted waste was saturated in water before mixing with other concrete components. The properties of the fresh mix were determined by slump method. The dynamic modulus of elasticity, flexural strength and compressive strength were tested on 28 days old concrete specimens. The σ-δ diagram is also presented. It was found that specimens with CKFW have better flexural strength and higher ductility but lower compressive strength than the reference concrete mix. The mix with the highest percentage of CKFW reduced the compressive strength by 28%, while the specimens with lower percentage of CKFW increased the flexural strength by 20% compared to the reference mix. The capillary water absorption capacity of concrete is closely related to its durability. The water absorption by capillarity was measured after 2, 4, 8, 15, 30, 45, 60 min, and 4 and 24 h. The increase in the amount of water absorbed was found to be higher than that of the reference mix. It was related to the percentage increase in the knitted waste and the values obtained ranged from 3.3 to 5.6% of the mass of the dry sample. The largest reduction in concrete density was 3.8% compared to the reference mix. Based on the obtained results, recommendations for further tests are given.