Striker Joshua King and goalkeeper Rob Elliot are both no longer with the Hornets.
King scored five goals in 31 Premier League appearances for Watford last season, after joining as a free agent.
Elliot’s two years at Vicarage Road, meanwhile, provided senior goalkeeping cover. His only first-team game time came early last season in the Carabao Cup.
“We wish both players well for the future,” Sporting Director Cristiano Giaretta said.
“In the case of Rob, he indicated he would wish to consider retirement but the decision is his now, of course.
“We are continuing to consider our options for the third goalkeeper and we need to make sensible choices with the Rule of 11 to consider.”