Mi liberty has been hired to help launch a range of consumer products in the UK market and modernise perceptions of the brand.
The company was previously a market leader, developing one of the world's first media players capable of streaming audio and video.
At height of its popularity, RealPlayer was sold as an extra with Windows 98.
But despite being downloaded more than 100 million times, the player has been affected in recent years by the success of Windows Media Player and Apple's iTunes.
Mi liberty managing director Dee Gibbs said: 'The company is famed for inventing the streaming media market and like most internet users I grew up with its RealPlayer.
'We will work with Real Networks to develop creative campaigns around the company's core consumer products such as RealPlayer, its online gaming site Gamehouse, and SuperPass, its subscription-based online entertainment service.'
The move by Real Networks to increase its UK presence follows the launch of its cloud service Unifi.
The company is aiming to compete with Apple's iCloud by allowing users to store digital content online on remote servers and access it from any device.