Hydrogen sulfide (H₂S) has traditionally been considered a toxic gas, but recent studies have revealed its role as a signaling molecule in plants. H₂S plays a crucial role in regulating cellular metabolism, seed germination, plant growth, development, and response to environmental stresses, including high temperature (HT) and low temperature (LT). H₂S can be synthesized and degraded in plant cells through enzymatic and non-enzymatic pathways, maintaining homeostasis. Despite the lack of identified plant receptors for H₂S, it exerts physiological functions through protein persulfidation. This review summarizes the current understanding of H₂S homeostasis, protein persulfidation, and the signaling role of H₂S in plant responses to HT and LT stress. The mechanisms involved include restoring biomembrane integrity, synthesizing stress proteins, enhancing antioxidant and methylglyoxal (MG) detoxification systems, improving water homeostasis, and reestablishing Ca²⁺ and acid-base balance. These findings provide insights into the physiological functions of H₂S and offer potential for developing temperature-stress-resistant crops to support sustainable food and agriculture.Hydrogen sulfide (H₂S) has traditionally been considered a toxic gas, but recent studies have revealed its role as a signaling molecule in plants. H₂S plays a crucial role in regulating cellular metabolism, seed germination, plant growth, development, and response to environmental stresses, including high temperature (HT) and low temperature (LT). H₂S can be synthesized and degraded in plant cells through enzymatic and non-enzymatic pathways, maintaining homeostasis. Despite the lack of identified plant receptors for H₂S, it exerts physiological functions through protein persulfidation. This review summarizes the current understanding of H₂S homeostasis, protein persulfidation, and the signaling role of H₂S in plant responses to HT and LT stress. The mechanisms involved include restoring biomembrane integrity, synthesizing stress proteins, enhancing antioxidant and methylglyoxal (MG) detoxification systems, improving water homeostasis, and reestablishing Ca²⁺ and acid-base balance. These findings provide insights into the physiological functions of H₂S and offer potential for developing temperature-stress-resistant crops to support sustainable food and agriculture.