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A red-emitting phosphor, CaY1-xEuxAl3O7 (CYA:Eu3+), was prepared by conventional solid-state reaction, and its structural properties were investigated by means of Rietveld refinement method and maximum entropy method using an X-ray source. XRD patterns confirm the tetragonal phase of CYA:Eu3+ phosphors. The photoluminescence properties of the samples were investigated for application to white light-emitting diodes (WLEDs). The emission spectrum is dominated by a red peak located at 616 nm due to the 5D0 → 7F2 electric dipole transition of Eu3+ ions. Concentration quenching occurs when the Eu3+ concentration is about 0.35 and the critical transfer distance of the phosphor is also calculated. A white LED fabricated with blue, green, and CYA:Eu3+ red phosphor incorporated with an encapsulant in ultraviolet LEDs (λmax = 396 nm) is discussed.