This article presents a reliability-based methodology for assessment of corrosion-affected, reinforced concrete sewers, considering serviceability and ultimate strength as limit state functions for multi-failure mode assessment. A stochastic model for system failure analysis is developed, which relates to key factors that affect concrete corrosion in a concrete sewer system in Harrogate in the United Kingdom. A time-dependent Monte Carlo simulation method is employed to quantify the probability of failure of concrete sewers with 70-cm diameter due to two categories of failure modes (serviceability and ultimate strength). Factors that affect the failure due to concrete corrosion are also studied by way of parametric sensitivity analysis.