The rate constant for electron attachment to Mo(CO)6 was determined to be ka = 2.4 ± 0.6 × 10−7 cm3 s−1 at 297 K in a flowing-afterglow Langmuir-probe experiment. The sole anion product is Mo(CO)5−. A small decline in ka was observed up to 450 K, and decomposition was apparent at higher temperatures. The charge transfer reaction of Ar+ with Mo(CO)6 is exothermic by 7.59 ± 0.03 eV, which appears to be sufficient to remove the first 5 ligands from Mo(CO)6+.