The Sm–Nd geochronology has great potential to directly constrain the age of hydrocarbon generation, migration, and charging; however, this technique has been rarely applied and poorly understood in the context of timing of petroleum system formation and evolution. In this contribution, we carried out a comprehensive study of the Sm–Nd isotope, mineralogical characteristics, and Raman spectroscopy of bitumen from the Erdaokan Ag–Pb–Zn hydrothermal deposit located in the arc basin of the northeastern Great Xing’an Range, northeastern China. Bitumen in the orebodies of the Erdaokan Ag–Pb–Zn deposit was formed coevally with the Ag–Pb–Zn mineralization and generally coexisted with galena, sphalerite, pyrargyrite, argentite, and pyrite mainly in the quartz veins. The Sm–Nd dating of the bitumen samples yielded an isochron age of 235.50 ± 2.18 Ma (uncertainty given as two standard deviations of the mean, n = 8, mean square weighted deviation = 0.095), which is consistent with the ages that were constrained by the pyrite–galena Rb–Sr technique (232.9 ± 2.3 Ma) and wall-rock zircon U–Pb dating (234.2 ± 2.8 Ma). Combining the formation temperature (170°C–200°C) and bitumen reflectance (0.72–0.87) estimated by the Raman spectrum parameter, we consider that the bitumen is similar to primary-oil solid bitumen, and the thermal cracking of the oil-prone organic matter from the source rocks during ore mineralization results in the formation of the bitumen. Therefore, the bitumen Sm–Nd age reflects the primary thermal-cracking time of oil-prone organic matter from the source rocks as well as the ore-formation age of the Erdaokan Ag–Pb–Zn deposit. Based on these findings, we strongly recommend the application of Sm–Nd isotope dating on hydrocarbon systems as well as hydrocarbon-bearing hydrothermal metal deposits.