“Is it obligatory upon new Muslims to change their previous names such as George, Joseph, and others?”
“It is not obligatory to change the name unless it means worshipping other than Allah. However, changing ones name to something better is permissible. Accordingly, changing ones name from a foreign name to an Islamic name is proper and good, but as to whether it is obligatory, no it is not.
But if a persons name is Abd Al-Masih (slave of the Messiah) or similar names that indicate servitude to other than Allah, it becomes obligatory to change it. It falls under the ruling of worshipping other than Allah by the Ijma (consensus) of scholars as reported by Abu Muhammad ibn Hazm (may Allah be merciful to him). Allah is the Grantor of success.
Answered by Shaykh ‘Abdul-‘Azeez bin Baaz
Reference: Volume 4, question 3.