Unity was awarded the ‘six-figure account’ on a retained basis for the rest of this year and 2020, following a four-way pitch process.
At the end of last month, Unity named a new managing partner and changed its consultancy model.
The Freesat brief includes developing activity that drives "meaningful brand awareness and consumer consideration through an on-going, integrated campaign and a series of ‘brand-fame’ moments in conjunction with other channels".
The agency said the campaign focus will be on engaging new audiences, elevating the brand’s prestige and promoting a significant new product launch in the coming months.
Freesat is a free-to-air satellite television joint venture between BBC and ITV, which also provides on-demand programming.
It is focusing on driving brand and market growth with "increased services, content and new technology".
"Unity understood the Freesat brand and the untapped potential surrounding it from the word go and demonstrated a unique creative approach, supported by a solid use of data," Freesat head of PR Amanda Willard said. "This is a huge year for us and we’re excited that they’re joining us on the journey."
Unity founder and CEO Gerry Hopkinson added: "Freesat is an incredible brand with a fantastic heritage and one that loves the best of British and global TV, past and present. It also understands the changing viewing habits and lifestyles of British consumers and the importance of blending great content with cutting-edge technology."