This paper presents the reliability assessment of reinforced concrete pylons for cable-supported bridges subjected to biaxial bending moment. The load contour method is employed to determine the strength of reinforced concrete pylons under biaxial bending. The failure surface defined by the load contour method is utilized as the limit state function in the reliability analysis. The load parameter and the strength parameter such as the material and geometric properties are considered as random variables. The most probable failure point and reliability index are calculated by the Hasofer-Lind Rackwitz-Fiessler algorithm with the gradient projection method for the advanced first-order second-moment reliability method. The reliability analyses of the pylon for cable-supported bridges in Korea are performed for the surface exponents of 1 and 2. The effect of the surface exponents and the comparison of the reliability index for uniaxial bending to that for biaxial bending are discussed in detail.