Tudor, 27, arrives from Surrey where he managed just one Championship appearance last season because of a career-threatening side injury.
After making his England debut in 1998, Tudor has played in 10 Test matches but never more than two in a row because of fitness problems and selection changes.
In all he has played just 67 first-class matches since making his Surrey debut as a 16-year-old in 1995.
But Tudor, who travelled to Munich for treatment, insisted Tuesday: "I am determined to repay Essex for the faith they have shown in me by regaining my top form in 2005. This is a new start for me and I am now just itching to get out on the field. My aim is to help Essex get promotion back to where they belong in the (first division of the) Championship."
Ronnie Irani, Essex's captain, said: "I am absolutely delighted with the world-class signing of Alex Tudor. Alex is an outstanding cricketer who will be a major factor with the new ball for Essex in the future."
Essex coach Graham Gooch, the former England captain, added: "This is a good signing for Essex because Alex has been a quality cricketer for Surrey and England. It goes without saying that he has had a few injury problems in the last couple of years but we are very hopeful of him making a major contribution when he gets back to full fitness."
"I was England manager on his first senior tour (Australia 1998-99) and I had nothing other than praise for the way he conducted himself - both on the field where he performed well in all three disciplines and in the dressing room."
"Alex is an international quality player and good team man who will be well motivated to prove his doubters wrong."
Tudor took a Test-best five for 44 against Australia at Trent Bridge in 2001 while his 99 not out in the Edgbaston Test against New Zealand in 1999 is an England record for a night-watchman.