The money was raised in a funding round led by the Royal Mail Group and backed by investors, including the Scottish Investment Bank, Par Equity and technology entrepreneurs.
Mallzee said the cash would allow it to "scale its global offering".
The company was founded in 2013 by 27-year-old Edinburgh-based entrepreneur Cally Russell.
Mr Russell pressed ahead with developing the app after turning down an offer of investment on the BBC's Dragons' Den programme.
Mallzee is a personalised shopping app, which allows users access to more than 100 fashion stores at one go.
It also lets shoppers build their own "style feeds".
Mr Russell said: "This round of investment is going to allow us to become the leading fashion shopping app in the world and the mix of investors is going to be vital to allowing us to achieve this.
"With Royal Mail Group we have a partner that plays a vital part in the online shopping environment and one which is well positioned to enable us to access new retailers."
Earlier this year, Mallzee secured an exclusive promotional link-up with tech giant Samsung.
In a separate development, daily fantasy sports operator FanDuel announced it had acquired Edinburgh-based mobile app developer Kotikan.
FanDuel said the firm had designed and developed its mobile offering and it was "logical" to bring the Kotikan team in-house to further innovate and develop FanDuel's mobile products.
FanDuel reported last week it was set for major expansion after raising $275m (£176m) in a funding round,
It was founded in Edinburgh in 2009 and only operates in North America.
The business focuses on US sports such as basketball, baseball and American football.

The 84 glass-fibre GoGoDragons! - all 5ft (1.6m) tall and which were part of a community art trail - were sold at The Forum in the city.
The auction raised £369,500 for charity Break, which cares for vulnerable people.
The dragons were painted by a variety of artists and in many styles.
One painted by 12-year-old art prodigy Kieron Williamson sold for £20,000, while a glittering mosaic dragon went for £25,000.
Dragons feature in much of Norwich's architecture and the city has churches dedicated to Saint George in Tombland and Colegate - both of which house dragon symbols.
The event follows on from 2013's GoGoGorillas! trail, which raised about £270,000 for charity at auction.
Fashion shopping app developer Mallzee is set to expand after securing £2.5m from investors.
[NEXT_CONCEPT]
Hundreds of thousands of pounds have been raised for charity by the sale of dragons that have been on display in Norwich.