Whittle follows National League South outfit Weston-super-Mare`s goalscoring midfielder Dayle Grubb in putting pen-to-paper on a move to The New Lawn earlier this month.
Twenty-four-year-old Whittle has agreed to sign until the end of the season, a move which will go through when the window opens on Monday.
The left-sided player is a former Liverpool academy youngster before being let go by the Premier League side at the start of 2011, having spent eleven years on the Red’s books.
In 2012, at the age of 19, Whittle signed a three-year contract with Scottish side Dunfermline Athletic, having trained with the Glenn Hoddle Academy and the Nike Academy during his time as an unattached player.
After being released by Dunfermline at the end of the 2014/15 season, the Liverpudlian played for AFC Fylde and Southport before joining newly-relegated York in May 2016 on a one-year contract, with the option of a further year, which was taken up.
Now with Forest Green, Whittle, who was capped by England Schools, is looking to prove himself in the Football League and says he is up for the challenge.
He told Forest Green`s official website: “I’m buzzing about the move.
“I’ve been waiting to get the chance to play in the Football League, so I’m delighted to get my chance.
“The philosophy of the style of play was a big selling factor for me. They always try to get the ball down and try and play.
“It worked well for them last season and I know they are trying to play that way again this season.
“I’ve just got to come in, work hard and I always give it my all and I hope to get my chance and take it”.