Traditionally, capacitor placement and conductor replacement have been considered as independent solutions for loss reduction in distribution networks. However, these two methods have an inherent coupling relationship, especially at harmonic frequencies. This work presents a joint optimization algorithm for both conductor replacement of overhead lines and capacitor placement to minimize energy losses in the presence of harmonics throughout the distribution system, such that both individual and total harmonic distortion of bus voltages are kept within the acceptable levels. All actual conditions including time varying nature of loads, network extension over the planning horizon, annual load growth and different load patterns are taken into account based on the realistic data. By applying the proposed method, the economic cost and energy losses are remarkably reduced compared to that could be achieved by applying these two methods separately in the presence of harmonics. The proposed method is applied on a realistic distribution network of Sirjan city-center in Iran.