Research is conducted to estimate uncertainty in concrete monoblock tie flexural behavior through Monte Carlo simulation. A parameterized Moment-Curvature based computational program was developed for design and analysis of the prestressed concrete monoblock tie flexural behavior. For Monte Carlo simulation, a parameter sweep was performed to sample the expected range of input quantities. The parameter sweep program generates independent parameter combination input files, and the quantities of interest (QOIs) are computed by the Moment-Curvature based computational program. The QOIs are computed at governing locations, including: 1) moment at first crack, 2) moment at crack propagation to outer layer of reinforcement, 3) deflection at rail-center and 4) crack height at AREMA recommended design force. Several simulation input parameters were randomly varied including 1) concrete compressive strength at 28 days, 2) initial concrete strength, 3) modulus of rupture, 4) prestress level, and 5) wire position. The results of the Monte Carlo simulation allow the estimation of the probabilistic prediction of tie performance. The prediction could be used to check primary tie design before proceeding to experimental tests for design approval. This approach could be used to analyze existing tie behavior, in track, for risk analysis.