AbstractA chemically vapor deposited MoS₂ nanosheets (NSs) is aged in the laboratory at ambient and at 40% average humidity for ~36 months. Nanorods of few microns in length and few nanometers in diameter are found to grow from the MoS₂ seeds. They have been growing as a result of the chemical reaction between the MoS₂ NSs and ambient O₂ and moisture, they exhibit an amorphous phase structure in the stoichiometric form of MoO₃. Density functional theory simulations further reveal the role of H₂O and O₂ in the transformation of the MoS₂ NSs. The adsorption energy of O₂ molecules on the MoS₂ sites is E_ad = −1.09 eV as compared to lowest absolute E_ad = −0.10 eV of H₂O indicating the favorable adsorption of O₂ and subsequent Mo oxidation. This study provides valuable insight into the aging phenomenon of MoS₂ exposed to O₂ and moisture which might limit their application.