Sandwich panels with carbon fiber reinforced plastics (CFRP) have high flexural strength-to-weight and stiffness-to-weight ratios and are used in structures requiring good mechanical properties, such as aircrafts and marine vehicles. In this study, the overall displacement of a sandwich panel with CFRP faces and an aluminum honeycomb core was reconstructed using the inverse finite element method (iFEM). The full in-plane strain fields were input into the iFEM and reproduced from the measured strains and an interpolation technique. We propose an interpolation method to calculate the overall strain fields on the sandwich panel based on strain distributions measured by fiber-optic sensors and numerically showed that the fully distributed sensing yields accurate and robust results in both strain and displacement reconstructions. To validate the proposed method, fiber-optic sensors were embedded in the sandwich panel, and strain distributions were measured by the sensing system with optical frequency domain reflectometry. In these experiments, we successfully and accurately measured the strain distributions along the embedded fibers and reconstructed the overall strain fields and displacement of the sandwich panel under four load cases. Furthermore, the sandwich panel shape identified by the proposed method can be employed for structural health monitoring.