City's managing director Karren Brady said: "We look forward to entering the new season with the backing of Phones 4u.
"The deal is much more than a shirt sponsorship package and I am sure the fans will welcome the news and support the range of initiatives that are being planned by Phones 4u and Birmingham City Football Club."
John Caudwell, chairman of Phones 4u, added: "Phones 4u is proud to be the new name on Birmingham City Football Club's shirts for the next two seasons.
Blues have kept with the traditional royal blue home colours and yellow away strip.
The home shirt includes the addition of a new white collar, a deep navy side flash under the arms and white piping.
The shorts are white with a royal blue side trim and the socks are royal blue.
The club decided to keep to the popular yellow for their away kit with the shirt including a blue zipped collar.
However, this time it is an all yellow strip following numerous requests from fans.
The launch of the home kit has been scheduled for Saturday 25th August.