Understanding the diffusion mechanisms of indium (In) in ZnS minerals can clarify the kinetic processes governing its migration, enrichment, or depletion in these typical In-host minerals, thereby establishing a theoretical foundation for the exploration of high-grade In deposits. This study investigates sphalerite and wurtzite to identify stable In incorporation sites and diffusion pathways, and systematically calculates In transport properties in two types of ZnS minerals using first-principles calculations combined with the climbing image-nudged elastic band (CI-NEB) method. The results demonstrate that structural anisotropy significantly governs In diffusion characteristics, with wurtzite exhibiting stronger direction-dependent diffusion behavior and superior In retention capacity compared to sphalerite. Across the 0−10 GPa pressure range, In diffusion in wurtzite shows markedly higher anisotropy (2−3 orders of magnitude greater than in sphalerite) and consistently lower diffusion rates. Furthermore, closure temperature calculations reveal spatial heterogeneity, with the [111] direction in sphalerite (about 65 K higher than [110] direction) and the [001] direction in wurtzite (about 100 K higher than [100] direction) displaying elevated closure thresholds. Overall, wurtzite achieves higher closure temperatures than sphalerite. These computational findings indicate that wurtzite exhibits stronger In retention capabilities than sphalerite, suggesting its potential as a critical host mineral for In. These insights provide valuable implications for understanding In geochemical cycling and offer some guidance for mineral exploration and ore genesis studies.