The theoretical investigations of interstitial tritium diffusion pathways in various Al-rich (>60% at. Al) iron aluminide coating phases found that in FeNiAl5 tritium prefers to diffuse in between layers, while in Fe4Al13, tritium prefers to diffuse across layers. In the case of Fe2Alx phases, the simulations show that the variable Al content in the channels affects the diffusion behavior of tritium in the channels. For 100% of vacancy, tritium prefers to diffuse at the center of the channel, while for 0% Al vacancy, tritium prefers to diffuse along the channel’s wall. In the case where 50% Al vacancy are present in the channels, tritium can diffuse in a mixed way, with positions oscillating between the channel’s center and wall. However, the large energy barrier involved in this case suggests that tritium diffusion could be correlated with Al diffusion in the channels. While we found that at 600 K interstitial tritium diffuses faster in Fe2Alx phases , then in Fe4Al13, and finally in FeNiAl5, we also find that interstitial tritium generally diffuses faster in Fe-Al coating phases than in ?-LiAlO2 pellets.