Mr Cashmore, 28, who set up the award-winning digital blog from the bedroom of his home in Banchory, Aberdeenshire at the age of 19, is reportedly planning to use the extra funding to fuel an expansion plan.
This is rumoured to include new areas of coverage of technology news and the opening of more offices, including in Los Angeles and London.
Reports last night said about $13.3 million (£8.1m)had been bought in equity by outside investors.
Mr Cashmore, who enjoys celebrity status, is to remain chief executive. He said: "We have a very exciting vision for what we can become as a media company. We absolutely believe that taking funding is the right way and the most effective way to achieve that vision," he said.
Mr Cashmore has previously considered selling Mashable, with reports linking the company to CNN in 2012. But he is understood to have since decided to build up the firm and made a number of key senior appointments last year.
"Last year was really about setting the groundwork," Mr Cashmore said.
"This year is about really ramping up aggressively and executing on the plan we drew up last year."
The investment round means the firm will be recruiting editors and advertising salespeople, with the chief operating officer suggesting a doubling of staffing levels. Mr Cashmore said the aim was to remain efficient and "do the absolute most with what we've got."