The Guardian and other newspapers have reported that GMG, the owner of The Guardian and The Observer, would appoint financial advisers within the next few weeks and a number of investment banks had already been approached.
The review would cover print classified, radio and regional newspaper assets and Trader Media is seen as a possible sale target, The Guardian said.
Trader Media publishes Auto Trader, Top Maruqes, AdTrader and Bike Trader, and owns websites such as autotrader.co.uk. It made an operating profit of £117m in the year to last April.
The review is also expected to determine whether GMG should retain and expand its radio assets, which include Smooth FM, or exit the sector.