Question: Is it permissible to recite Kaddish for a non-Jewish friend?

Answer: Yes, it’s permissible if the mourner feels a sense of gratitude or connection to their non-Jewish friend. This is discussed in Zechor LaAsot (Ma’arechet Tav, Siman 81) and seems to align with the opinion of HaRav Ovadia Yosef zt”l (Yecheveh Da’at (Part 6, Siman 60), where he permits Kaddish to be said for a non-Jewish father. The principle can be extended to a non-Jewish friend if there was a sense of kindness or benefit received, and the mourner feels a strong emotional need to do so. It’s worth noting, however, that the Vashav VeRafa (Part 6, Siman 2:9) cites HaRav Aharon Leib Steinman zt”l, who expressed that reciting Kaddish would not help the non-Jewish soul. For further insight, see Shu”t Vayeshev HaYam (Part 3, Siman 38).