© 2020 Elsevier LtdWe have investigated the device characteristics of a Ti2CT2 (T = O or F) MXene-based field-effect transistor consisting of semiconducting Ti2CO2 seamlessly connected to metallic Ti2CF2 electrodes. Our non-equilibrium Green's function (NEGF) quantum transport calculations reveal that the smallest feature size is ≈6 nm for gate-controlled current. Changing the surface termination alters the electronic states in such a way that the transmission is blocked in an energy window wider than the fundamental energy gap of Ti2CO2. The positive gate voltages increase the current, while the negative values have the opposite effect. As the surface terminations of the electrodes are not crucial, modification of the termination only in the scattering region is sufficient. The ultrathin Ti2CT2 MXene-based nanodevices are thus feasible candidates for efficient field-effect transistors.