The trio will become legal directors in the government and infrastructure department, it said.
BDB added that the move would increase the number of specialists in the department to 28, "making it the largest planning team under one roof for any UK law firm".
The three have experience delivering major infrastructure and planning projects, the statement said, including energy, highways and urban transit.
They also have "extensive experience of Parliamentary processes and are actively involved in advising on HS2".
Nick Brown, BDB partner and head of department, said: "We are naturally very pleased to welcome Ian, Sarah and Tom back to BDB.
"All are extremely talented, client-focused lawyers and their return adds significant capability to the department.
"It has been a busy and successful 12 months. We have continued our work with existing clients such as National Grid and Peel Holdings, as well as securing new appointments, including a place on the Highways Agency legal panel.
"Having all three of our colleagues back will further cement our position as the natural choice for infrastructure and general planning advice."
Cameron, Clark and Henderson moved to Pinsent Masons last July along with Duncan O’Connor and Francis Tyrrell.
They followed former BDB partner Robbie Owen who joined Pinsent Mason's infrastructure, planning and government affairs division a month earlier.
A spokesman for Pinsent Masons said: "Three lawyers are leaving the planning team to join Bircham Dyson Bell and we wish them well.
"We are the largest planning team in the UK by some margin, with over 85 lawyers, and we continue to grow.
"As part of this, our Infrastructure Planning, Parliamentary and Government Affairs capabilities have gone from strength to strength since Robbie Owen and others joined our market leading team last year.
"We are excited about our prospects for the year ahead."