The former Page 3 girl will bow out to pursue new projects when her current contract expires in March, The Sun reports.
In a statement, Messenger said that she has had a "fantastic" time on Five's evening programme, which is also presented by ex-footballer Ian Wright and Apprentice finalist Kate Walsh.
A Five spokesman commented: "We would like to thank Melinda for the great job she has done."
It is thought that Messenger will be replaced by a series of guest hosts, including Hollyoaks actor Ricky Whittle and GMTV's Gloria De Piero, who have both filled in on the show before.
Insiders have suggested that reality star Walsh recently agreed to renew her own contract with Studio Five for a further six months.