Establishing the New Zealand Transport Agency cost $2.8m, figures released to Radio New Zealand reveal.
The agency was formed in August by merging Land Transport New Zealand and Transit New Zealand.
Figures obtained under the Official Information Act show more than $1m was spent on support and advice for the merger, with another $500,000 on rebranding.
The agency's spokesperson Andy Knackstedt says it was fair to devote such resources to the merger, given the agency has 1300 staff and offices in 13 centres.
Institution of Professional Engineers policy director Tim Davin says the cost of establishing the agency is a fraction of its $3bn annual budget.
The agency is now re-structuring as a result of the merger.
The Public Service Association, which has been briefed about the changes, says the number of jobs remain unchanged.