Paul hartley agreed a deal with the 21-year-old late on Thursday afternoon.
The versatile player has played in a number of positions but has been deemed a forward by Falkirk.
He has spent time on loan at Crawley Town (pictured) and Woking.
Paul Hartley, the Bairns boss told falkirkfc.co.uk: “We are absolutely delighted to be able to secure the signing of a player of Dennon’s calibre. He is an exciting, young talent who is extremely quick and I am certain that he is a player that will get the fans off their seats.
“Dennon is a player that has been on our radar for some time, he has proved highly sought after amongst clubs in the Championship and League One in England so we are thrilled to have been able to get him signed up and to have him with us for the start of pre-season.
“We are very pleased with all of our business so far both in terms of our new signings and contract extensions. This is a very exciting time for the football club and we look forward to having more positive news in the near future.”
Lewis is the third new recruit at the Bairns following similar pre-contract signings of Patrick Brough and Tom Dallison.
Louis Longridge and Sean Welsh won’t be returning to the club though. Talks with Craig Sibbald are understood to be ongoing.