You can, But you have to send a ticket to support here -
http://support.chess.com/index.php
PLEASE READ FIRST:
If you would like to change your Chess.com username, please include three usernames you'd like, in order of preference, and as long as they available, the name can be changed the name for you. NOTE: We will only change your username for you one time!
Please note that you cannot have any spaces or dots in the name, nor any special characters like dots or ^ & * ! " £ $ % ( ) + = ? / \ |
hello, i would like to change my user name can you help me, please?