The Beipiao Formation in western Liaoning, northeastern China, represents one of the most important Early Jurassic organic-rich successions and is widely regarded as a potential source rock for hydrocarbons. However, the absence of robust radioisotopic age constraints has long hindered accurate stratigraphic correlation, source rock evaluation, and regional paleoenvironmental reconstruction. In this study, zircon U–Pb isotopic dating of a well-preserved volcanic ash layer interbedded within the lower coal-bearing interval of the Beipiao Formation yields a weighted mean age of 187.04 ± 0.98 Ma, providing the first reliable absolute age anchor for this formation. The new age constrains the main depositional interval of the Beipiao Formation to the Pliensbachian–Toarcian, broadly consistent with existing but poorly-constrained biostratigraphic evidence. This refined chronology thus supports the interpretation that the distinctive thick organic-rich mudstones in the upper Beipiao Formation were likely coeval with the well-known early Toarcian hyperthermal event (i.e., the Jenkyns Event). These results establish a temporal framework for future assessments of hydrocarbon generation potential of the Beipiao Formation and the response of continental lacustrine systems to Early Jurassic climatic perturbation.