In this article, we fabricated Y₂Ti₂O₇: Yb, Er, Tm upconversion inverse opal photonic crystals with energy transfer between Er³⁺ and Tm³⁺, and investigated the influence of the photonic band gap on the energy transfer between Tm³⁺ and Er³⁺. It is interesting that strong modification of the steady state upconversion emission spectra is observed, and the green or red upconversion emission from Er³⁺ was suppressed in the inverse opal. More significantly, the energy transfer between Tm³⁺ and Er³⁺ is enhanced by suppression of the red upconversion emission of Er³⁺, thus the blue upconversion emission from Tm³⁺ is considerably improved in the inverse opals. Additionally, the mechanisms for upconversion emission of the Y₂Ti₂O₇: Yb, Er, Tm inverse opal are discussed. We believe that the present work will be valuable for the foundational study of upconversion emission modification and the application of upconversion displays and short wavelength upconversion lasers.