Terrorist Nationality Act of 2014 - Amends the Immigration and Nationality Act to include among the grounds for loss of U.S. nationality by a native-born or naturalized citizen:

• taking an oath or making a declaration of allegiance to a foreign terrorist organization after attaining the age of 18;
• entering or serving in a foreign terrorist organization or the armed forces of a foreign state if such armed forces or foreign terrorist organizations are engaged in hostilities or acts of terror against the United States or U.S. nationals; and
• becoming a member of or providing training or material assistance to any foreign terrorist organization that such person knows, or has reason to know, will engage in hostilities against the United States or will commit acts of terror against the United States or U.S. nationals.

(Eliminates the grounds for loss of U.S. nationality by entering or serving in the armed forces of a foreign state if such armed forces are engaged in hostilities against the United States, or by serving as a commissioned or non-commissioned officer in such armed forces.)