The Gejiu tin polymetallic deposit, located in the southwest margin of the South China Belt bordering on the Yangtze Block, is hosted in Triassic carbonates. This study shows that there is an indium enrichment in the ores.Indium mainly exists in sphalerite-rich massive sulfide ores with a concentration of 198.3–1570 ppm; the indium concentration in sphalerite ranges from 493.3 up to4781 ppm. The inferred indium reserve in the Gejiu Sn deposit is over 4000 t, indicating that the Gejiu tin deposit is a giant In-bearing Sn-polymetallic deposit, similar to the Dachang and Dulong in southwest China. Sphalerite with a high Fe value(8.05–13.27 wt%) is the predominant indium carrier mineral; meanwhile chalcopyrite plays the secondary indium carrier role. EPMA mapping result shows that indium is likely distributed homogeneously and presented as a substitution for Zn in sphalerite. The Gejiu tin polymetallic deposit, located in the southwest margin of the South China Belt bordering on the Yangtze Block, is hosted in Triassic carbonates. This study shows that there is an indium enrichment in the ores. Indium mainly exists in sphalerite-rich massive sulfide ores with a concentration of 198.3-1570 ppm; the indium concentration in sphalerite ranges from 493.3 up to 4781 ppm. The inferred indium reserve in the Gejiu Sn deposit is over 4000 t, indicating that the Gejiu tin deposit is a giant In-bearing Sn- polymetallic deposit, similar to the Dachang and Dulong in southwest China. Sphalerite with a high Fe value (8.05-13.27 wt%) is the predominant indium carrier mineral; whilewhile chalcopyrite plays the secondary indium carrier role. EPMA mapping result shows that indium is likely distributed homogeneously and presented as a substitution for Zn in sphalerite.