Head Coach Richard Hill said: "We're obviously disappointed that Graham Kitchener will leave the club at the end of the season.
"He has come through the Warriors Academy system and progressed to the England Saxons squad through his performances and development at Sixways.
"Graham remains a key part of our squad and will continue to represent the Warriors throughout the remainder of the season in the RFU Championship play-offs and British & Irish Cup.
"He is an outstanding professional and I have no doubt that he will continue conduct himself in the right manner and do everything he possibly can to help the club gain promotion.
"We have been very active with the recruitment of second rows as we build for next season. We now look forward to revealing to our supporters the new recruits, who boast a wealth of experience and talent in this position, in the coming week."
Kitchener said: "This was obviously a very tough decision to make as I feel a great sense of loyalty to everyone at the club who has helped me to progress from an early age. However, after much deliberation I feel the time is right to give myself a new challenge.
"I would like to thank everyone involved at the club, especially Andrew Stanley and Gary Meechan who have always guided and helped me and Phil Davies who has taken a lot of time in mentoring me individually this year. All of this input has been invaluable to me.
"The fans have also always been great and I have been humbled by how many have told me of their desire for me to stay, which made the decision even harder to take.
"For now, though, my only focus is playing as big a part as I can in helping the club secure promotion for next season."