A wide range of materials for the development of new products can be obtained from natural resources. Good examples of these materials are lignocellulosic wastes, which are a good alternative for the production of particleboards. This study aimed to evaluate the feasibility of using cotton wastes in association to eucalyptus particles in the production of particleboards. Cotton waste proportions used were 0, 10, 20 and 30%. Urea formaldehyde (UF) adhesive was applied at 12%, based on dry the weight of particles. Physical and mechanical tests were performed in order to evaluate panels. Water Absorption (2 and 24 h) and Internal Bond (IB) showed not significant effect with increased percentage of cotton waste. Thickness Swelling (2 and 24 h) of particleboards increased with increased percentage of waste material. The Modulus of Elasticity for cotton waste particleboards ranged from 726.47 ± 99.98 to 205.12 ± 66.24 MPa, while the Modulus of Rupture ranged from 8.63 ± 1.39 to 3.87 ± 0.75 MPa. According to results, cotton wastes could be added to particleboards up to the percentage of 9%, being indicated for the manufacture of some types of furniture such as doors and sides.