For a long time, molecular electrocatalysts have been developed to reduce CO2 efficiently to value-added products such as CO and HCO2H, along with H2; however, selectivity remained as a major issue. Recent work toward addressing this issue showed that several different catalysts could be used to achieve product selectivity. It is desirable that instead of using different catalysts for specific products, a single catalyst should be able to produce the target products by subtle tuning of the reaction conditions. Toward this objective, herein we presented the organometallic Co electrocatalyst Co-NHCU and successfully utilized it in the electrochemical CO2 reduction reaction (CO2RR) to produce CO, H2, and HCO2H with notable selectivity. The reduction of CO2 selectively produced CO with 81 ± 2% Faradaic efficiency (FE) in the presence of 5% H2O as a proton source. The selectivity was changed toward H2 with 80 ± 3% FE when 1.5 M triethylamine was added as an additive in the presence of 10% H2O as a proton source. In the presence of 1.0 M morpholine as an external additive, the CO2-saturated solution containing 10% trifluoroethanol as a proton source generates 55 ± 5% HCO2H as the predominant product, with H2 as a competitive side product. It was found that the combined effect of the proton source and the additive in association with the nature of the Co-NHCU catalyst changed the selectivity of the products in this reaction.