We found that substitution of not only a larger ion like Ba2+ [J. Am. Ceram. Soc., 93, 138 (2010)] but also a smaller one like Mg2+ (this paper) replacing no >14.9% Ca2+ ions could enhance integrated down-shifting (DS) emission intensity of red phosphor Ca3(VO4)2:0.12Eu3+, indicating that both lattice expansion and contraction can decrease the site symmetry of Eu3+ in Ca3(VO4)2:0.12Eu3+ phosphor. This finding is anticipated to improve the Eu3+ emission intensity of other Eu3+–doped phosphors. To further investigate Eu3+ up-conversion (UC) behaviors, Yb3+ ion was used as a sensitizer. Interestingly, 5D1 → 7F3,4,6 transitions of Eu3+, which were barely detectable under DS excitation, exhibited strong intensity under UC excitation. A “recycling” process, arising from the 5D1 → 7F3 transition of Eu3+ and cross-relaxation Eu3+ (7F3) + Eu3+ (5D0) → Eu3+ (7F0) + Eu3+ (5D1), is presumably the leading mechanism of such inconsistency.