The role of epithermal effects in muon catalyzed fusion specially in the H/D/T mixture is investigated by Monte Carlo method. The results of the Monte Carlo simulation are used in the kinetics of μCF in the steady-state condition. For this purpose we determine the values of thermalization rate (λth) and the probability of the dtμ molecular formation by epithermal tμ atoms during thermalization processes (η parameter). We have shown that including the epithermal effects in the kinetics of μCF in different concentrations of hydrogen isotopes, increases the fusion yield per muon and it is not ignorable even in the D/T mixture. The reduction of the μCF efficiency due to increasing the protium concentration is definitely confirmed here, even though the important effects such as the epithermal molecular formation, Ramsauer–Townsend effect and the hyperfine interactions are taken into account. We have shown that the epithermal effects disappear rapidly, whereas the unfavorable effects due to increasing protium, such as highly sticking probability in the pdμ and ptμ cycles, affect the fusion yield for a longer period of time. Recent experimental results at JINR in the H/D/T mixture are compatible with our conclusions.