<p>Gd³⁺-sensitized Tb³⁺-based glasses are high light-yield scintillators. Energy transfer sensitization between Gd³⁺ and Tb³⁺ is well-recognized. Gd³⁺ ions are also found to typically modulate the interionic distances of Tb³⁺ ions; however, the mechanism why this effect enhances the latter’s photo luminescence still remains unclear. This work focuses on Gd³⁺, Tb³⁺ co-doped La₂O₃-B₂O₃-SiO₂ (LBSO), first demonstrating Tb³⁺ clusters via spectroscopy. LBSO’s optimal Tb³⁺ single-doping concentration is 37%, rising to 50% with 20%Gd³⁺. The LBSO:20%Gd³⁺,50%Tb³⁺ sample exhibits a 542 nm emission intensity 2.22 times that of the 37%Tb³⁺ single-doped sample, 38% scintillation efficiency (vs. BGO), and &gt; 20 lp mm⁻¹ X-ray resolution. The introduction of Gd³⁺ increases the interionic distance between Tb³⁺ ions within the clusters, thereby suppressing the concentration quenching effect and enhancing the fluorescence emission. We propose this mechanism as “cluster-dispersion sensitization effect”. This effect was further confirmed in other glass systems (LBSO:Lu³⁺, Tb³⁺, LBSO:Y³⁺, Tb³⁺, Bi-based:Lu³⁺, Tb³⁺, etc.). Spectroscopic analysis shows Gd³⁺-Tb³⁺ energy transfer efficiency up to 80%. In conclusion, Gd³⁺ synergistically enhances Tb³⁺ fluorescence via both effects. These findings not only fully elucidate the sensitization mechanism of Gd³⁺ ions in Gd³⁺, Tb³⁺ co-doped scintillating glasses but also provide new insights for researching the manipulation of activator ion clusters in luminescent materials. In search for novel scintillators, cluster-dispersion sensitization effect may greatly improve their spatial resolution via intrinsic artichtectures design in glasses, ceramics, thin films, and nanoparticles.</p>