Mechanical behaviors in multilayered two-dimensional decagonal quasicrystal (QC) circular nanoplates with initial stresses and nanoscale interactions including electrostatic and Casimir forces are investigated using the state space approach. A uniform static initial biasing field with the initial stresses and related electric displacement for the piezoelectric phase is considered in this research. The external voltage and no voltage between the nanoplate and substrate is respectively applied to the model with QC/crystal/QC structure. The electromechanical coupling characteristics of the model are numerically calculated for different nonlocal scale parameters, initial gaps, initial stresses, and nanoscale interactions. Results indicate that all responses in the phonon, phason, and electric fields are positively influenced by the attraction between the substrate and nanoplate under the Casimir force. The effect from Casimir force is more significant than the effect produced by the electrostatic force under the applied external voltage. The initial compressive stress can reduce displacement and increase electric displacement and Casimir force. Besides, the effect of initial compressive stress is not as evident as the Casimir effect, which determines loading conditions.