A fast simulation method is proposed for accurate performance evaluation of error control coded systems. The proposed method, iterative flat histogram two-phase algorithm (IFH-TPA), addresses the issue of long simulation times required by Monte Carlo (MC) simulations to estimate very low error probabilities. IFH-TPA employs Wang-Landau (WL) flat histogram Monte Carlo method for efficient sampling of rare events that lead to bit errors in decoded sequences. A Viterbi decoder simulation scenario validates that IFH-TPA can provide sample size reductions in the order of 1000 in estimating error rates as low as 10 −9 for a rate 1/2 convolutional code of constraint length 7 in AWGN channels. Further, IFH-TPA estimations agree well with MC estimations and the union bound of the code.