In this study, the raw materials of BaCO3 and ZrO2 powders with different average diameters were used to prepare BaZrO3:Eu0.025 phosphors by the solid-state reaction method. The raw materials with different average diameters were prepared by mixing them by the ball milling method and/or grinding them in a nanoscale grinding machine. As different grinding processes were used, the BaCO3 and ZrO2 powders had the average diameters of 2124, 707, 645, and 496 nm. When raw materials with the average diameter of 2124 nm were used and the calcination temperature was changed from 1100 to 1400 °C, the BaZrO3:Eu0.025 phosphors showed two strong orange emission bands with peaks at the wavelengths of 574 and 596 nm and two weak emission bands with peaks at 620 and 650 nm. The maximum intensity of the emission spectrum of the BaZrO3:Eu0.025 phosphors increased with increasing calcination temperature. When the raw materials with the average particle sizes of 707, 645, and 496 nm were used and the calcination temperature was changed from 950 to 1150 °C, the BaZrO3:Eu0.025 phosphors showed one broad blue emission band with central wavelengths located at 464–466 nm. In this study, we prove that when the sizes of the source materials are different, the luminescence properties of the BaZrO3:Eu0.025 phosphors will have large variations after they are calcined at different temperatures.