We investigated the optical properties of La2Zr2O7 transparent ceramics and found that it showed abnormal partial dispersion. The origin of the abnormal partial dispersion was also investigated by measuring the vacuum ultraviolet reflectance and infrared absorption and by performing first-principle calculations. All the measurements and calculations were also performed on LaAlO3Sr(Al,Ta)O3 and Ba(Zr,Mg,Ta)O3 transparent ceramics, which showed normal dispersion, for comparison purposes. A comparison of the measurements and calculations with the numerical investigations carried out using a dispersion equation indicated that a weak intensity of absorption of La2Zr2O7 in the high energy region (20–30 eV) was thought to be the predominant reason for the abnormality. In addition, a narrower bandwidth of the O-2p band of La2Zr2O7 resulted in a high intensity of absorption around 10 eV, which in turn resulted in a relatively low ratio of the intensity of absorption between 20 and 30 eV to the intensity of absorption around 10 eV. This narrower bandwidth of O-2p was thought to augment the abnormality of La2Zr2O7.