She joins as campaigning and public affairs manager, reporting to director of comms and campaigning Sarah Talbot-Williams.
Bird was previously policy officer for European cancer information charity Cancerbackup.
CLIC Sargent has been expanding its communications team since the merger of CLIC and Sargent Cancer Care in 2005.
Bird replaces David Webster, who held the role as an interim consultant.
She said she would attempt to make children's cancer ‘a political priority'.