Immigration New Zealand has announced the closure of its Dunedin and Sydney offices, as well as a management restructure.
The Public Service Association says that up to nine other offices including two overseas are also to be reviewed which could lead to further closures.
PSA assistant secretary Basil Prestidge said staff have been briefed on the changes.
Mr Prestige said the proposal will lead to about 25 job losses initially, with the likelihood of more in the future.
The changes are being driven by the introduction of new technology and the Government's drive to deliver public services online.