Introduction: The gut microbiota plays an important role in host environmental adaptation, including defense against pathogens. Parasite infections can disrupt gut microbial communities and thus influence host adaptability. However, most current knowledge of Blastocystis-microbiota interactions comes from humans or domestic animals, and data from wild mammals, especially those inhabiting extreme environments, remain scarce. Methods: In this study, we analyzed 68 gut metagenomes from Tibetan antelopes (Pantholops hodgsonii) and screened for infections by four intestinal parasites - Blastocystis, Cryptosporidium, Giardia, and Encephalitozoon bieneusi. Results: Among them, 26 individuals were solely infected with Blastocystis subtype ST31. Compositional analysis revealed 25 differential families, with 12 enriched in infected and 13 in healthy individuals. LEfSe further identified 38 species-level biomarkers (LDA > 2, p < 0.05), indicating a significant shift in gut microbial diversity following Blastocystis ST31 infection. Notably, the relative abundance of Arthrobacter sp. 08Y14, associated with environmental resilience, was markedly reduced in infected individuals. Functional profiling showed a decrease in metabolic diversity, with 18 CAZy families detected in the healthy group but only 2 in the infected group. KEGG analysis showed that the average relative abundance of K07497 was higher in the infected group (5.16) than in the healthy group (1.03). Discussion: These findings suggest that Blastocystis ST31 infection reshapes the gut microbiota and may impair the high-altitude adaptability of Tibetan antelopes by reducing plateau-adaptive microbes and functional capacity. This study provides the first evidence of Blastocystis-induced gut microbiota changes in Tibetan antelopes and broadens our understanding of parasite-microbiota interactions across hosts.