Precise is headquartered in London and has offices in New York and works for 2,500 customers including large and small companies, PR agencies and public sector bodies.
The value of the transaction was not disclosed, but WPP said that Precise generated £28.9m in revenues for the year ending 30 September 2013.
Kantar Media has bought control of Precise after a number of smaller acquisitions over the past two years to strengthen its media monitoring offer, including social TV analytics company The Data Republic in April, Singapore-based media monitoring service Fisheye Analytics in December 2013 and French media monitoring service Press Index in 2012.
The decision to sell by Precise, which was founded in 1996, was made during an active period in PR services mergers and acquisitions.
Vocus and Cision have been bought by the same private equity company and are expected to be combined, while Gorkana has been reported to be up for sale.