Two-dimensional (2D) nanomaterials with tunable electronic and magnetic properties are promising for their versatile applications in multifunctional devices. In this work, we present a first-principles study on the electronic and magnetic transitions of 2D Ti2NO2 monolayer achieved by applying tension. We show that 2D Ti2NO2 experiences a transition from ferromagnetic half-metal to antiferromagnetic semiconductor as tension increases up to a certain level. We find that charge redistribution occurs with the extension of bond length due to the suppressed crystal field splitting. We further show that the charge transfer between eg and t2g orbitals gives rise to the shift of the energy levels and opens a gap near the Fermi level, resulting in the electronic transition. The semiconducting nature favors the superexchange coupling, leading to the magnetic transition from the ferromagnetic state to the antiferromagnetic state. We expect that the 2D Ti2NO2 monolayer with tunable electronic and magnetic properties may find applications in nanodevices, such as spintronics and sensors.