Carrying banners such as "Telecom give your customers service" and "Jobs before profits", the engineers marched about 1.5km from Britomart to Telecom's Auckland head office on Hereford St.
The vocal crowd blew horns as they demonstrated outside, chanted slogans and heckled staff members who were leaving for lunch.
The march was part of a second round of strikes scheduled for today and tomorrow by about 900 Downer EDi Engineering and Transfield Services employees contracted to provide line maintenance work.
They are protesting as Telecom's network division Chorus moves to an owner-operator model following the signing of a 10-year contract with Visionstream in Auckland and Northland.
The Engineering Printing and Manufacturers Union (EPMU), which is representing the workers, said the workers were striking for redundancy protection.
EPMU campaigner Joe Gallagher said the issue was the "continuing desecration of the industry by Telecom".
Workers who did not become owner-operators contracted to Visionstream would essentially be made redundant by Telecom, he said.
"In most cases they'll only get four weeks notice and then they'll be on the scrap heap, because most of these guys can't afford to go into this model." Mr Gallagher expected the action would result in faults building up on the network, particularly in Auckland.
Chorus chief executive Mark Ratcliffe said not all line engineers would end up becoming owner-operators as, of the three companies Telecom has contracts with, only Visionstream works with the owner-operator system.
"Visionstream are taking over in Northland and Auckland, that's about 40 percent of the workforce." He said the company's owner-operator policy was not the reason it won the Telecom contract.