Big staff reductions have prompted Telecom to leave one of its four buildings at its Victoria St headquarters in Auckland.
Jim Robb of Telecom property projects said the business no longer needed four towers in the campus-style property.
"You will no doubt be aware that there has been staffing realignment at Telecom," Robb said.
"We are now in the position where we can operate from three of the four towers so Telecom's about to advertise one complete tower of about 6,500sqm for sublease or assignment."
Telecom is shedding between 930 and 1,230 staff.