The FMCG giant has 23 agencies working on its digital and direct communications.
It has issued a brief to agencies saying it is assessing its needs.
The review, which is a procurement-led process, is being overseen by Rachel Bristow, the head of direct communications and new media. Bristow joined Unilever from Sainsbury's last year.
The review will affect all DM and digital agencies on the roster.
Digital agencies include Dare, which handles Lynx, and glue London, which works on Impulse.
On the DM side, Claydon Heeley Jones Mason works on Impulse and Craik Jones Watson Mitchell Voelkel works on brands including Carte D'Or, Bertolli and Birds Eye. It also won the customer relationship marketing for Hellmann's Extra Light mayonnaise. Chemistry and Tullo Marshall Warren are also on the roster, working on Dove and Comfort respectively.
Unilever is already holding a roster pitch for the DM business for its Vaseline Intensive Care range.