Shennan’s exit follows a profit warning at the contractor last week.
The move will now see civil engineering head Nick Fletcher and construction boss Pat Boyle report directly to group chief executive John Morgan.
A Morgan Sindall spokesperson said: “We’ve taken a detailed look at how we run the Construction and Infrastructure division in order to create a more efficient company for growth.
“We have taken the decision to create a flatter structure, with Pat Boyle and Nick Fletcher, Managing Directors of our Construction & Design and Infrastructure activities respectively, reporting directly into John Morgan, Group Chief Executive.
“Pat and Nick are working closely together to deliver complex, integrated projects for our clients which draw on our Construction and Infrastructure expertise.
“As a result of these changes, the role of Managing Director of Morgan Sindall plc has been made redundant and Graham Shennan has left the business.”