Cadwallader joins Harlequins wing Ben Gollings and Bristol lock Garath Archer in joining the Falcons, who have also tied down a whole host of their current crop.
Those to prolong their stay at Kingston Park are England stars Jonny Wilkinson, Jamie Noon and Dave Walder, as well as fellow backs Tom May in the centres, England XV fullback Michael Stephenson, former All Black centre Mark Mayerhofler and scrum-half Hall Charlton.
In the forwards, Scotland openside Andrew Mower has stayed with the club, as has prop Micky Ward, South African prop Marius Hurter, England XV captain and No.8 Hugh Vyvyan, prop Ian Peel, England Sevens forward Phil Dowson and back rower John Dunbar.
Newcastle's Director of Rugby Rob Andrew said of his squad: "Last season was a real roller-coaster ride for the Newcastle Falcons. We started the season poorly and had to work hard to finish the season on a high having secured Premiership status.
"During the summer we have refocused our thoughts and brought in Alex, Garath and Ben to further strengthen the team. We are looking forward to the challenges ahead of us and are confident of a much improved season in 2003-2004."
The 1998 champions will face pre-season matches against Glasgow on August 22 in Scotland, as well as at the Llanelli Scarlets on August 29, following their appearance at the Middlesex Sevens on August 16.
By Mark Smith