The magnetic and optical properties of Ce-doped ZnO systems have been widely studied; the effects of different strains on Ce-doped ZnO systems with O or Zn vacancies remain unclear. This study identified the effects of biaxial strain on the magnetic and optical properties of Ce-doped ZnO systems with O or Zn vacancies through a generalized gradient approximation + U method. Zn15CeO15 showed the best stability among Ce-doped ZnO systems with O vacancies when the distance between Ce atoms and O vacancies was 0.3801 nm. Zn14CeO16 showed the best stability among Ce-doped ZnO systems with Zn vacancies when the distance between Ce atoms and Zn vacancies was 0.3249 nm. The formation energy of Zn15CeO15 and Zn14CeO16 first increased and then decreased with increasing compressive strain, whereas that of Zn15CeO15 and Zn14CeO16 decreased with increasing tensile strain. The band gap of Zn15CeO16 and Zn14CeO16 widened and the absorption spectra blueshifted with increasing compressive strain. These findings will help with the design and preparation of new ZnO-based short-wavelength light-emitting diodes. The band gap of Zn15CeO16 and Zn14CeO16 narrowed and the absorption spectra redshifted with increasing tensile strain. These findings help with the design and preparation of novel ZnO-based photocatalysts. Zn15CeO16 and Zn14CeO16 showed room-temperature ferromagnetism in the absence of strain. The magnetic moments and Curie temperature of Zn15CeO16 and Zn14CeO16 decreased with increasing compressive and tensile strains. The Zn15CeO16 system was antiferromagnetic under - 5% compressive strain, whereas Zn14CeO16 system was antiferromagnetic under - 4% and - 5% compressive strain, and 4% and 5% tensile strain. The magnetic moment, Curie temperature, and ferromagnetism-antiferromagnetism of Zn15CeO16 and Zn14CeO16 can be controlled by strain. These results can serve as a reference for the design and preparation of Ce-doped ZnO magnetic materials and magnetic switches.