Time Out has sold a 50 per cent stake in the business to Bermuda-based private equity firm Oakley Capital Investments.
The undisclosed investment from the AIM-listed company marks the end of a lengthy search for capital by the magazine's founder Tony Elliott.
Elliott said: "I have considered many potential investors over the last seven years to help the brand with the next phase of development and I believe that Oakley Capital, with its entrepreneurial operational focus, will help us with this.
'I genuinely believe that I have found a real partner for what I expect to be a hugely successful worldwide digital journey."
Time Out, which was founded in 1968, now has operations in over 30 countries around the world publishing entertainment and cultural guides and information through a network of 36 city magazines, an online and mobile presence, 22 travel guides and a portfolio of events and other partnerships.
In March, Time Out was appointed as the official publisher of travel guides for the London 2012 Olympic Games and Paralympic Games and the brand now has an estimated worldwide audience of over 17m annually with over 2m in London.
Oakley Capital said this morning that its role would be to provide financial and strategic support for the growth of the Time Out across all print and digital channels.
Peter Dubens, director of Oakley Capital Investments, said: "It is very rare to be able to help with such a renowned, iconic brand as Time Out, which over the last 42 years has provided first class editorial on culture and entertainment to over 50 cities around the world.
'We believe that we will help this brand both in its traditional media and the continued transition to digital over the coming years."
According to the most recent figures available from the UK's Audit Bureau of Circulations, Time Out has an average weekly circulation of 58,275 during the first half of the year.