Is It Permissible for a Man to Wear a Necklace?

Hello,

If it is a necklace that is designated for men, then as a matter of strict halacha there is no prohibition involved (Deuteronomy 22:5), "A man shall not wear a woman’s garment." In any event, in most places men do not customarily wear a necklace.

Sources: See the book Paat Zechakha (page 120) in the name of Rabbi Nissim Karelitz zt"l. See also Responsa Igrot Moshe, Even HaEzer, part 4 (siman 32, section 2), and the book Ohr L'Tzion, part 2 (chapter 23, section 11). See also the book Mincha L'Chaim (page 143).

With blessings,

Hillel Meirs