Currently developments of piezocomposite materials and piezoelectric actuators have been based on the use of simple analytical models, test of prototypes, and analysis using the finite element method (FEM), usually limiting the problem to a parametric optimization. By changing the topology of these devices or their components, we may obtain an improvement in their performance characteristics. Based on this idea, this work, discusses the application of topology optimization combined with the homogenization method and FEM for designing piezocomposite materials and piezoelectric actuators. The homogenization method allows us to calculate the effective properties of a composite material knowing its unit cell topology. In the design of piezocomposites, new effective Properties that improves the electromechanical efficiency of the piezocomposite material are obtained by designing the piezocomposite unit cell. Prototypes of the optimized piezocomposites were manufactured and experimental results confirmed the improvement. In the design of piezoelectric actuators, we focus on the low frequency flextensional actuators which consist of a piezoceramic connected to a coupling structure that converts and amplifies the piezoceramic output displacement. By designing new kinds of coupling structure flextensional actuators for different tasks can be obtained.