In this study, we investigated the resistive switching (RS) behavior of Pt/Nb-doped SrTiO3 (Pt/Nb:STO) single-crystal junctions in air and vacuum. We performed steady-state electrical characterizations: the direct current (DC) currentvoltage relationship and relaxation currenttime dependence under an applied voltage step. The ideality factor of the junction suggested the existence of interface states and tunneling current. We observed that the relaxation current followed the Curievon Schweidler law; electrical conduction was dominated by a space-charge-limited current based on charge recombination at the interface states. The dynamic electric response was obtained using an alternating current (AC) conductance technique. The carrier lifetime at the interface traps was largely dependent on the resistance state and the ambient environment. Thus, surface potential modification by charge capture/release at the interface traps played a crucial role in the RS of our junctions. Additionally, the ambient effect showed that oxygen desorption (adsorption) at the Nb:STO surface increased (decreased) the interface state density. Finally, an RS model based on interface states in Pt/Nb:STO was proposed.