Walker's move has been clinched following what Bath describe "as a result of co-operation with the RFU (Rugby Football Union)," and he is due to link up with them in November after the current rugby league season finishes.
The 23-year-old back has represented Great Britain and England, while also helping Leeds to the 2004 Super League title and World Club Challenge crown when Rhinos defeated Canterbury Bulldogs last year.
Walker boasts a league strike-rate of almost one try every two games, and he follows former Great Britain captain Andy Farrell into the union code, although injury has so far denied Saracens recruit Farrell his 15-a-side debut.
Farrell's move has so far proved a disappointment for the RFU, given his injury problems, but it has not deterred them from playing a role in Walker switching codes to potentially work with England supremo Andy Robinson and red rose attack coach Brian Ashton, who quit Bath barely a week ago.
Walker said: "After eight seasons with Leeds Rhinos, it is time for a new challenge with the end of my Rhinos contract coinciding with my 24th birthday.
"Rugby union offers a new stage at club, and potentially, international level. Having decided to switch codes, Bath offers the promise of an exciting brand of rugby at a traditional union club with a great heritage.
"England coach Andy Robinson and Brian Ashton, as the then Bath coach, have become inspirational mentors, and I look forward to working with them in the England camp as well as the new coaching staff at Bath and the rest of the Bath squad."
Walker clearly has strong ambitions to emulate the likes of dual-code English internationals Jason Robinson and Henry Paul, who both played for Bath on short-term contracts nine years ago, and a 2007 World Cup squad place is his undoubted target.
"Chev is a young player with proven skills in the cauldron of Super League," said Bath rugby director and former England coach Jack Rowell.
"He has made a strong impact in rugby league, and is now coming to rugby union. He is a quick, powerful and skilful player who will reinforce the Bath Rugby back line.
"He is joining a great club, and he will have one eye on translating his talents on to the international field with England.
"However, patience will be needed with Chev as it will take time for him to adapt to rugby union, as other players who have crossed between the codes have shown."