The food, cosmetics and womenswear departments will be revamped to reach more families and the 'grown-up lady'.
The landmark Bullring store has been praised for its design, but criticised by some observers for failing to match the needs of local consumers.
A Selfridges spokeswoman refuted speculation that the store has not fulfilled expectations. 'We are very pleased with the store's performance,' she said. 'We're always developing the offer and moving on in all our stores.'
Work will begin on the womenswear department within the next few weeks. A wall will be knocked down to make it easier for the customer to navigate their way around the shop. The existing wine, confectionery and grocery departments will double in size and stock more of the ranges available in the Oxford Street branch.
Work is due to be completed by mid-November.