The ${\text{TiO}}_2:{\text{Sm}}^{3+}$ inverse opal has been prepared by a template-assisted method, and its modification on photoluminescent (PL) properties of ${\text{Sm}}^{3+}$ is studied. Transmittance spectra show a dip within the photonic bandgap, whose location shifts a little to red and then to blue with an increasing detection angle between the incident light and the surface normal; such an irregular shift is attributed to uneven shrinkage of lattices. Steady-state PL spectra indicate a spatial redistribution of emission lines. Decay kinetics demonstrate that the spontaneous emission rates of ${\text{Sm}}^{3+}$ ions in the inverse opal decrease to varied extent depending on the emission wavelength and detection angle. All the facts are examined to be consistent with the photonic bandgap effect.