The major mononuclear aluminum species obtained in the reaction of aluminum atoms with dimethyl sulfide (DMS) and diethyl sulfide (DES), under cryogenic conditions, are the C-S insertion products, CHAlSCH and CHCHAlSCHCH, respectively, showing that aluminum atoms can activate C-S bonds. The magnetic parameters were extracted from the EPR spectrum. Support for the spectral assignment was obtained by repeating the experiments with C-labeled dimethyl sulfide yieldingCHAlSCH. DFT calculations using the M06 functional have proven to be effective in predicting the isotropic and anisotropic Al hyperfine interaction values of the aluminum atom C-S insertion products. In addition, the thioalkyl radicals, CHSCH and CHCHSCHCH were formed in the aluminum atom reaction.