Over 50 billion cells undergo apoptosis each day in an adult human to maintain immune homeostasis. Hydrogen sulfide (HS) is also required to safeguard the function of immune response. However, it is unknown whether apoptosis regulates HS production. Here, we show that apoptosis-deficient MRL/lpr (B6.MRL-Faslpr/J) and Bim (B6.129S1-Bcl2l11tm1.1Ast/J) mice exhibit significantly reduced HS levels along with aberrant differentiation of Th17 cells, which can be rescued by the additional HS. Moreover, apoptotic cells and vesicles (apoVs) express key HS-generating enzymes and generate a significant amount of HS, indicating that apoptotic metabolism is an important source of HS. Mechanistically, HS sulfhydrates selenoprotein F (Sep15) to promote signal transducer and activator of transcription 1 (STAT1) phosphorylation and suppress STAT3 phosphorylation, leading to the inhibition of Th17 cell differentiation. Taken together, this study reveals a previously unknown role of apoptosis in maintaining HS homeostasis and the unique role of HS in regulating Th17 cell differentiation via sulfhydration of Sep15.