Slack has raised $427 million in Series H funding and is now valued at $7.1 billion.
The latest cash comes from Dragoneer Investment Group and General Atlantic, and is in addition to the $841 million the company has raised since its launch in 2013.
The workplace communications app currently claims to have eight million daily active users across 500,000 organisations, as well as three million paid users.
Slack has been under attack over the last couple of years, with Microsoft and Facebook both launching competing products.
In a blog posted on its website, Slack said: “We pursued this additional investment to give us even more resources and flexibility to better serve our customers, evolve our business, and take advantage of the massive opportunity in front of us.”
The US-based company is becoming increasingly global, with more than half of its users now coming from outside of the US.
Italy is Slack’s fastest growing market outside of America, while Japan has recently surpassed the UK as the firm’s second largest market, based on the number of daily active users.
