Piezoelectric sensors and actuators have gained considerable interest by investigators and researchers for their use in intelligent/smart structures and electromechanical systems. Furthermore, demands from industry for sensors and actuators with higher quality and better performance for a variety of applications have lead the researchers to design piezoelectric systems with optimal configurations to enhance the performance of such actuators and sensors. An analytical micromechanics approach is presented to model the effective longitudinal mechanical properties of Metal-Core Piezoelectric Fibers (MPFs) and Macro Fiber Composites (MFCs). The model assumes general orthotropic material properties for both outside and inside materials. Next, using constitutive equations, the exact analytical solutions for the stress distributions are obtained for axially loaded active fibers. To examine the mechanical performance of the MPF and MFC, material properties and geometric dimensions are substituted into the analytical exact solutions and then effective longitudinal mechanical properties as well as the stress distributions within the domain of each constituent material are obtained and then compared. Finally, the results are presented and concluding remarks are addressed and discussed in details.