Forest boss Joe Kinnear is close to completing a deal to bring the midfielder to the City Ground on a month's loan.
The 30-year-old will travel to Nottingham tomorrow to discuss personal terms and could make his debut against Bradford City on Saturday.
Barmby has only made three appearances this season for Leeds and the former England international can count Liverpool, Everton, Middlesbrough and Spurs among his former clubs.
Barmby joined Leeds in August 2002 for £2.75m but has failed to establish himself as a regular at Elland Road.