Efficient and selective earth-abundant catalysts are highly desirable to drive the electrochemical conversion of CO2 into value-added chemicals. In this work, a low-cost Sn modified N-doped carbon nanofiber hybrid catalyst is developed for switchable CO2 electroreduction in aqueous medium via a straightforward electrospinning technique coupled with a pyrolysis process. The electrocatalytic performance can be tuned by the structure of Sn species on the N-doped carbon nanofibers. Sn nanoparticles drive efficient formate formation with a high current density of 11 mA cm(-2) and a faradaic efficiency of 62% at a moderate overpotential of 690 mV. Atomically dispersed Sn species promote conversion of CO2 to CO with a high faradaic efficiency of 91% at a low overpotential of 490 mV. The interaction between Sn species and pyridinic-N may play an important role in tuning the catalytic activity and selectivity of these two materials.