Aliovalently-doped zirconia (ZrO2) systems such as yttria-stabilized ZrO2 (YSZ) have been explored as ionic conductors for solid oxide fuel cells (SOFCs) owing to their high ionic conductivity and exceptional mechanical and chemical stability. Thin film micro-SOFCs (μ-SOFCs) with free-standing membranes create an opportunity for reduced temperature operation with the need to engineer the various materials components. In this study, we have fabricated μ-SOFCs composed of nominally pure ZrO2 electrolytes (down to sub-10 nm thickness) prepared by room temperature photon-assisted oxidation of Zr precursor metal films and nanoporous Pt electrodes and report on fuel cell performance up to ∼500 °C in hydrogen. The μ-SOFCs exhibit maximum power density of ∼33 mW cm−2 with open circuit voltage of ∼0.91 V at 450 °C. The electrolyte thickness-dependent functional properties of the μ-SOFCs are discussed in detail along with thermo-mechanical stability and microstructural studies. The results could serve as a benchmark to understand doping effects in designing thin film fast-ion conducting zirconia-based electrolytes for low temperature fuel cell operation.