A gentile – Sheva Mitzvos: According to the Rishonim who rule that the age of 13 is a tradition of Moshe from Sinai, then it is possible that this age does not apply to a gentile. However, according to the reason of maturity which is learned from Shimon and Levi, then since it is a matter of nature, it seemingly applies also to a gentile.<a href="#_ftn1" name="_ftnref1">[1]</a> According to this approach, gentiles become Bar Mitzvah at age 20 or 21, which is the age that he is fit to go to war.<a href="#_ftn2" name="_ftnref2">[2]</a>
<a href="#_ftnref1" name="_ftn1">[1]</a> Igros Kodesh 5:76, brought in Shulchan Menachem 3:333; See Likkutei Sichos 10:70
<a href="#_ftnref2" name="_ftn2">[2]</a> Reshimos Choveres 19

Shulchan Aruch HaRav | 📄 When does a gentile become Bar Mitzvah?

A gentile – Sheva Mitzvos: According to the Rishonim who rule that the age of 13 is a tradition of Moshe from Sinai, then it is possible that this age does not apply to a gentile. However, according to the reason of maturity which is learned from Shimon and Levi