The 31-year-old has played 285 top-flight games across Australia and England, with 34 coming for the Canberra Raiders and another 32 for the Tigers.
“We have been in the market for an experienced forward with the ability to play either in the middle or on an edge,” Cowboys General Manager of Football Micheal Luck said.
“John bases his game around defensive intent and willingness to compete in every situation – a couple of areas we've made no secret we want to improve significantly on in 2025.
“Along with what he does on the field, we also believe he will be a valuable mentor for our younger forwards in Heilum Luki, Jeremiah Nanai and Griffin Neame.”
A 27-time England international, Bateman's departure will allow the Tigers to free up a spot in their Top 30 roster, which is set to be handed to Sione Fainu.
Debuting in Round 11, 2024, at Magic Round against The Dolphins, Fainu finished the season with 12 first-grade appearances and showed that he has all the qualities of an NRL player, just like his two younger brothers.
Scoring two tries during these matches, the club has confirmed he will remain at the Wests Tigers, inking a train and trial contract.
Starting his career at the Manly Sea Eagles, Sione was the first member of his family to move to the Tigers and is a former U19s NSW Blues representative in his own right.