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.
Fashion shopping app developer Mallzee is set to expand after securing £2.5m from investors.