The Mailbox claims to have bucked national trends after announcing a 13 per cent rise sales in first half compared to 2004.
This compared to a first half increase of just three per cent between 2003 and 2004, after the retail venue struggled to attract customers away from the newly-opened Bullring.
Natalie Strachan, the Mailbox retail director, said: "People who may have originally been attracted to the Bullring have started to find their way around the rest of Birmingham.
"Now the whole city benefits from the increase in shoppers."
The Mailbox also saw sales for January rise 32 per cent compared to the same period last year, although growth has slowed over the summer months.
Mrs Strachan said: "The general economic conditions, terrorism and the city centre evacuation have knocked consumer confidence.
"This has affected every retailer in Birmingham to some degree, including The Mailbox.
"However, we are seeing footfall return and expect sales growth to have risen significantly by the fourth quarter."
In June, the Mailbox announced plans for a new, £60 million, 500,000 square foot extension called The Cube.
Proposals for the building are expected to be submitted for planning permission later this summer.