The effects of 1,5-pentanediol (PDO) and N, N-Bis (hydroxyethyl) aniline (ISL) chain extenders on the mechanical and adhesion properties of the polyurethane adhesives based on hydroxyl-terminated polybutadiene were studied. Results showed that both chain extenders (ISL and PDO) improved the adhesion properties of the polyurethane on the aluminum substrate. The peel test modulus increased significantly in the presence of both chain extenders. The increase was more pronounced using PDO chain extender (the one with aromatic side group). A decrease in contact angle and an increase in work of adhesion were obtained by addition of chain extenders to the polyurethane. The glass transition temperature of the PU did not change significantly in the presence of chain extenders. However, the cross-linking density and toughness of the polyurethane increased significantly by addition of the chain extenders. Results showed that chain extender without side chain (PDO) improved the adhesion as well as the mechanical properties of the polyurethane much greater than the one with aromatic side ring.