AbstractAll‐solid‐state batteries (ASSBs) show great potential as high‐energy and high‐power energy‐storage devices but their attainable energy/power density at room temperature is severely reduced because of the sluggish kinetics of lithium‐ion transport. Here a thermally modulated current collector (TMCC) is reported, which can rapidly cold‐start ASSBs from room temperature to operating temperatures (70–90 °C) in less than 1 min, and simultaneously enhance the transient peak power density by 15‐fold compared to one without heating. This TMCC is prepared by integrating a uniform, ultrathin (≈200 nm) nickel layer as a thermal modulator within an ultralight polymer‐based current collector. By isolating the thermal modulator from the ion/electron pathway of ASSBs, it can provide fast, stable heat control yet does not interfere with regular battery operation. Moreover, this ultrathin (13.2 µm) TMCC effectively shortens the heat‐transfer pathway, minimizes heat losses, and mitigates the formation of local hot spots. The simulated heating energy consumption can be as low as ≈3.94% of the total battery energy. This TMCC design with good tunability opens new frontiers toward smart energy‐storage devices in the future from the current collector perspective.