Increasingly, efforts have been made to replace adhesives that contain formaldehyde in their formulation with others free of this substance in the production of engineered wood. It is known that the release of formaldehyde can cause serious problems to human health, potentially leading to death. As a result, the use of formaldehyde-free adhesives has gained prominence in industries. Furthermore, a major challenge in the use of wood products refers to their durability, which can be reduced by the attack of xylophagous agents. The use of preservative solutions is an alternative that mitigates this problem and guarantees greater durability to the material. Therefore, the objective of this work was to evaluate the mechanical properties of glulam beams produced with rubberwood treated with preservatives chromated copper borate (CCB) and pyrethroid using polyurethane as adhesive, a type of free-formaldehyde adhesive. The glulam beams were produced with 3 lamellas measuring 60 × 20 × 1200 mm, differentiated by the type of adhesive (polyurethane and resorcinol-formaldehyde), and by the presence or absence of preservative treatment. Specimens were obtained from the beams for characterization regarding resistance to normal compression, structural compression, and compression parallel to the fibers in dry and wet conditions. Among the properties evaluated, it was found that preservative treatments did not affect the compressive strength parallel to the fibers in beams produced with polyurethane, with values of 33.77 and 31.61 MPa for those without treatment and treated with CCB, respectively, not showing significant differences. These results show the potential for using polyurethane as an adhesive in glulam beams.