A kinetic Monte Carlo model of a reversible addition–fragmentation chain transfer (RAFT) process is presented. The algorithm has been developed and implemented in Julia for the three main RAFT theories under current discussion (slow fragmentation, intermediate radical termination, and intermediate radical termination with oligomers). Julia is a modern programming language designed to achieve high performance in numerical and scientific computing. Thanks to a careful optimization of the code, it is possible to simulate a RAFT reaction scheme in short computing times for any of the three theories. The code is benchmarked against other programming languages (MATLAB, Python, FORTRAN, and C), showing that Julia presents advantages for this particular system. The model offers an efficient method for predicting average properties and molecular weight distributions of the polymer species, including the bivariate molecular weight distribution of the intermediate two-arm adduct. The proposed model can also be employed to obtain additional detailed information regarding the polymer microstructure at any reaction time.