New Zealand Post says posties' days off due to injury have halved since brightly-coloured safety gear was introduced.
However, the posties' union says the figures have been massaged more than injured workers' limbs.
In April 2008, the company issued high-visibility helmets and mail bags to go with fluorescent clothing that posties were wearing.
Since then, 50 posties have been hurt badly enough to need time off - down from 106 the previous year.
The Postal Workers' Federation says the figures are being massaged, as members are pressured to return to light duties - or even fake jobs.
It says posties face peer pressure, as bonuses are cancelled if too much time is lost.
But New Zealand Post says total safety incidents, including near-misses, are also falling.