The transition piece of a fixed offshore wind turbine is a reinforced part of the support structure that is connected to the wind turbine tower. These structural elements present unique features and are critical components of offshore wind turbines; designed to resist strong bending moments, shear forces and axial loads coming from cyclic environmental loads, such as wind and wave loads, acting during their complete design life of 20 years. Well designed and manufactured transition pieces with optimized ultimate and fatigue capacities, contribute to the structural soundness and reliability of offshore wind turbines. In this paper we investigate the benefits of integrating structural topology optimization in the design process of these elements, specially compared to classical design processes that are strongly based in experience and trial-and-error heuristic procedures. We first develop a solution for a 5 MW reference wind turbine with a jacket support using the classical design process and then apply structural topology optimization techniques to the same design problem. After verification of both solutions, it was found that the optimized solution is lighter and presents hot spots with lower stresses that extend its fatigue life significantly; demonstrating that an integrated design cycle that includes topology optimization can be very effective, speeding up the total design cycle and increasing the reliability of the final product. (c) 2015 Published by Elsevier Ltd.