The protocol of micro-flow nucleophilic pentafluoroethylation using pentafluoroethane (HC2F5, HFC-125), a nontoxic, inexpensive, and commercially available greenhouse gas, is described. The micro-flow pentafluoroethylation by HFC-125 proceeded smoothly at room temperature or at −10 °C in DMF or toluene in the presence of a potassium base, namely, t-BuOK or KHMDS. A broad range of ketones, aldehydes