Transparent microwave absorbers that exhibit high optical transmittance and microwave absorption capability are ideal, although having a fixed absorption performance limits their applicability. Here, a simple, transparent, and thermally tunable microwave absorber is proposed, based on a patterned vanadium dioxide (VO₂) film. Numerical calculations and experiments demonstrate that the proposed VO₂ absorber has a high optical transmittance of 84.9% at 620 nm; its reflection loss at 15.06 GHz can be thermally tuned from –4.257 to –60.179 dB, and near-unity absorption is achieved at 523.75 K. Adjusting only the patterned VO₂ film duty cycle can change the temperature of near-unity absorption. Our VO₂ absorber has a simple composition, a high optical transmittance, a thermally tunable microwave absorption performance, a large modulation depth, and an adjustable temperature tuning range, making it promising for application in tunable sensors, thermal emitters, modulators, thermal imaging, bolometers, and photovoltaic devices.