Quantum-mechanical effects on the electron captures by protons from hydrogenic ions are investigated in semiclassical dense high-temperature plasmas. An effective pseudopotential model taking into account both the quantum-mechanical effects and the plasma screening effects is applied to describe the projectile–electron interactions in dense high-temperature plasmas. The semiclassical version of the Bohr–Lindhard model has been applied to obtain the electron capture radius and the electron capture probability. The impact parameter method is applied to the motion of the projectile proton in order to visualize the electron capture probability as a function of the impact parameter, thermal de Broglie wavelength, Debye length, and projectile energy. The results show that the quantum-mechanical effect reduces the electron capture cross section. It is also found that the electron capture probability significantly decreases with a slight increase of the quantum-mechanical effect through the thermal de Broglie wavelength.