Source-gated transistors (SGTs) with Schottky barriers have emerged as extraordinary candidates for constructing low-power electronics by virtue of device simplicity, high gain, and low operation voltages. In this work, we demonstrate flexible low-power SGTs with solution processed In₂O₃ channels and Al₂O₃ gate dielectrics on ultrathin polymer substrates, exhibiting light area density (0.56 mg cm⁻²), low subthreshold swing (102 mV dec⁻¹), low operation voltage (<2 V), fast saturation behaviors (0.2 V), and low power consumption (46.3 μW cm⁻²). These achievements pave the way for employing the unconventional SGTs in wearable applications where low-power dissipation and high mechanical flexibility are essential.