Heat stress is a major concern for livestock production, as it can result in reduced animal welfare, decreased production efficiency, and even mortality. MicroRNAs (miRNAs) are small non-coding RNA molecules that play a critical role in regulating gene expression and have been proposed as potential biomarkers for heat stress in livestock. Several studies have investigated the expression of miRNAs in response to heat stress in various livestock species, including cattle, pigs, and chickens. These studies have identified specific miRNAs differentially expressed in response to heat stress, suggesting they could serve as biomarkers for this condition. For example, in cattle, miR-21, miR-23a, miR-24, miR-27a, miR-30a-5p, and miR-126 have been shown to be upregulated in response to heat stress, while miR-122, miR-127, miR-148a, miR-195, and miR-335 were downregulated. In pigs, miR-23a, miR-26a, miR-27a, miR-27b, miR-34a, and miR-146a were upregulated, and miR-let7f, miR-let7i, miR-29c, miR-30c, miR-143, miR-148a, and miR-221 were downregulated in response to heat stress. In chickens, miR-22, miR-23a, miR-27a, miR-30a-5p, miR-92a, miR-146a, and miR-155 were upregulated, while miR-let-7f and miR-181a were downregulated. In conclusion, miRNAs have shown promise as potential biomarkers for heat stress. In addition, it is necessary to validate these findings and explore their potential use in developing diagnostic tools for monitoring heat stress in livestock.