The critically acclaimed actress will play the feisty Julie Perkins, whose arrival on Albert Square turns Billy Mitchell's (Perry Fenwick) life upside down as she forces him to face some shocking home truths.
Speaking about the role, Murphy said: "Like our characters, I've known Perry since I was 16 and he is a brilliant actor. We've never worked together before so I am looking forward to getting stuck into our fantastic rollercoaster of a story."
The arrival of Julie, described as an "antidote to the snarling women of Albert Square", will leave Billy stunned to discover that he may have more skeletons in the closet waiting to be discovered.
Julie will be Murphy's third role in the BBC soap. She previously appeared in 1997 and more recently in 2005 as Trisha Taylor - the mother of Leo, who fathered Demi Miller's baby.