This paper describes the use of a new polymer entrapment flash pyrolysis (PEFP) method for making nanoscale yttrium ruthenate (Y2Ru2O7‐δ) electrocatalysts. This approach effectively reduced the synthesis temperature of phase‐pure pyrochlore catalysts from 1000 °C to 550 °C, and greatly suppressed the sintering of catalyst particles. The supported nanocrystalline Y2Ru2O7‐δ catalysts showed enhanced activity towards oxygen evolution reaction (OER) in acidic electrolyte and were stable at 1.50 V for the comparative study (>20 h) under the current density of 10 mA/cm2geo in chronopotentiometry testing. This is equivalent to an overpotential value of 270 mV, about half of that of the reference IrO2 catalyst. X‐ray absorption spectroscopy (XAS) and transmission electron microscopy (TEM) analysis showed that the high‐surface‐area Y2Ru2O7‐δ catalyst had an oxygen‐deficient structure. This study provides a route to the synthesis of fine ceramic (or oxide)‐based electrocatalysts for making high‐performing electrocatalysts.