The linear and nonlinear aeroelastic characteristics of a Strut-Braced Wing for large transport aircrafts are investigated. The Strut-Braced Wing is a design that goes back to the dawn of aviation and still continues to be widely used in small general aircraft. The concept for using the Strut-Braced Wing for large passenger aircraft has been around since the 1940's, and it has been shown that this wing configuration has several advantages over a conventional cantilever wing. Although several aeroelastic studies have been performed on Strut-Braced Wings, the effects of structural nonlinearities have not been fully investigated. In this study, the linear and nonlinear flutter and divergence speeds are determined for two different configurations. The two configurations were selected to highlight the effect that the joint location has on the aeroelastic results. The first configuration has the lower wing connecting at the midpoint of the upper wing and the second configuration has the lower wing connecting at the tip of the upper wing. The aeroelastic analysis is performed using NASTRAN and an in-house program. It was found that for the first configuration, the geometric nonlinearity significantly affects the aeroelastic performance and an increase of the flutter speed is observed compared to the linear case. The second configuration, the geometric nonlinearity negatively impacts the dynamic aeroelastic stability and the flutter speed is reduced with respect to the linear case. It is concluded that the structural geometric nonlinearity must be included even in the preliminary aeroelastic investigations of this type of configurations to have meaningful evaluation of the aeroelastic response and stability analysis.