Richard Cockerill will leave as England forwards coach after the Six Nations to join French club Montpellier.
Saracens forwards coach Ian Peel is expected to replace the 52-year-old.
Cockerill was the only remaining assistant coach from Eddie Jones' reign after Steve Borthwick succeeded the Australian as head coach in December.
The former England hooker joined the staff in September 2021 and said it was "an honour" to have played for and coached his country.
Cockerill won 27 England caps in his playing career and was briefly interim head coach following Jones' sacking.
After five wins from 12 Tests in 2022, Borthwick is attempting to rebuild the side before the World Cup that begins in France in September.
That process began with a narrow defeat by Scotland in their Six Nations opener at Twickenham on Saturday, after which Borthwick acknowledged failings in England's set-piece.
Former Newcastle forward Peel was former head coach of England Under-20s.
Cockerill, who was head coach of French side Toulon and "always had aspirations to return" to work in the Top14, said: "This opportunity presented itself some time ago.
"It is disappointing not to work with Steve and the wider team beyond the Six Nations. I had hoped to be able to stay for the Rugby World Cup, but the timings weren't meant to be.
"I will continue to be fully focused on England and this Six Nations campaign, working with this group of players as they begin a new journey together.
"It's exciting to see what change has happened so far in such a short period of time."
Borthwick described Cockerill as "an excellent coach" and added: "It was a difficult decision for him to leave and he has our support."
Analysis - 'More coaching upheaval'
BBC rugby union correspondent Chris Jones
While England's forward play was mixed during his tenure, Cockerill was a popular figure with the players, with Borthwick hailing his "invaluable support and guidance".
Cockerill's departure will lead to even more coaching upheaval, but this is perhaps an unavoidable consequence of the RFU making a regime change when they did, with Borthwick understandably keen to bring his own staff in.
It means Borthwick will have a full coaching team of his own in time for the Rugby World Cup, although we wait for confirmation on Cockerill's replacement - expected to be Ian Peel - as well as clarity on who will be the attack coach long-term, with Nick Evans currently working on a short-term basis.