The seven figure media account covers The Daily Mirror, Sunday Mirror and The People.
A shortlist for the pitch is currently being drawn up, and will include incumbent agency ZenithOptimedia.
Lorraine Fraser, Marketing Director Trinity Mirror Nationals, said: "We have had a strong working relationship with ZenithOptimedia for many years now, however we feel the time is right for this review as it will ensure that our media planning and buying strategies remain as competitive and creative as possible.
"Over the past 18 months the Daily Mirror and Mirror.co.uk have undergone fundamental redesigns, The People has been redesigned and all our national papers now have full colour. On top of this we have recently launched two new standalone sites, Mirrorfootball.co.uk and 3am.co.uk.
"Our portfolio is very different to what it was 15 years ago and our media buying strategy must reflect both the dynamism and heritage of our highly prestigious national brands."
A decision on the review will be made by the end of the year.
