Tehran, the capital of Iran, lies in a highly active seismic zone and is exposed to significant earthquake risk due to multiple nearby faults. Among critical urban infrastructure, gas distribution network is especially vulnerable to earthquakes, but it has not been thoroughly studied in most current risk assessments. This study proposes a probabilistic framework to evaluate the seismic vulnerability of Tehran’s gas distribution network under four major earthquake scenarios (Mosha, North Tehran Fault, Eyvanakey, and Rey faults). The methodology incorporates both aleatory and epistemic uncertainties from hazard and damage assessment of buried pipelines and pressure reduction stations. The intra-event variability of ground motion values is considered in the analysis through random sampling from spatial-cross correlation model. Similarly, the aleatory uncertainty of damage types (leak and break) in pipelines is captured in the analysis through random sampling from probabilistic distribution. Results from 1,000 Monte Carlo simulations reveal that the Eyvanakey scenario poses the highest risk, particularly in southeastern Tehran, while the Rey scenario results in minimum damage. The spatial distribution of risk underscores the importance of localized mitigation strategies. The proposed framework provides an appropriate tool for urban seismic risk assessment and resilience planning of gas utility system in seismically active cities.