Yeates made 30 appearances last season for the losing play-off finalists while Bonham had a senior debut to forget as the Hornets lost 2-1 to Leeds on the final day.
Prince Buaben, Stephen McGinn, Piero Mingoia, Aaron Tumwa and Stephan Hamilton-Forbes will also leave Vicarage Road when their contracts expire while Chris Iwelumo has already joined Scunthorpe.
"The Hornets would like to place on record its thanks to all players for their contribution during their time at the club, and wish them all the best in their future careers," a statement on the club's official website said.
- Sports & Recreation
- Piero Mingoia
- Chris Iwelumo