In this letter, the Invasive Weed Optimization (IWO) method is applied to design and optimize a printed Yagi antenna. The optimization goals are set to reach an antenna with a VSWR less than 1.5 and a high-gain radiation pattern. The fitness function is calculated by FEKO, which uses the method of moments for evaluating the structures. By implementing this simple closed-loop algorithm, the best available structure has been achieved compared to the results of the previous studies. Finally, a <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> -band optimized version of the antenna is fabricated and tested. The experimental data are in good agreement with the simulation results, which verifies the performance of the IWO method.