The remote Kirwans Hut in the Victoria Forest Park, northeast of Reefton, is on the historic Kirwans Track, a two to three day 40km circuit for experienced trampers.
Department of Conservation Western South Island operations director Mark Davies said the hut damage was found by a visitor in January.
The 12-bed hut, built in the 1980s, has reopened after DoC field staff undertook repairs recently.
Mr Davies said the damage included swastikas being painted on the roof and external walls.
"Whoever did the damage took paint stored on site to daub swastikas on the hut roof and external walls, as well as the water tank," he said.
The vandals also smeared paint on the inside of a new toilet, broke the toilet lid, smashed the hut guttering that feeds the hut's water tank, and broke part of the boardwalk to the toilet.
It came less than a year after the Backcountry Trust undertook a major revamp of the hut, including a new coloursteel roof as one of their Jobs for Nature projects.
"The damage is senseless, sickening and extremely disappointing for DoC, the Backcountry Trust which upgraded the hut, and trampers using the facility," Mr Davies said.
In March 2023, four trust volunteers undertook the upgrade over four days, which took 200 hours of labour.
"I know the team was particularly proud of how well the hut came up through their efforts."
Mr Davies said Kirwans is a popular hut and used a lot over summer.
"Our DOC team put in a great deal of effort in the leadup to Christmas to ensure it was accessible."
DoC staff removed the swastikas and repaired the damage, including painting over the new roof as there was no other way to remove the graffiti.
Mr Davies said the cleanup was costly as it took staff away from other essential work.
Victoria Forest Park is the largest park of its type in the country with a network of tracks, many dating back to mining days and with relics scattered amid regenerating forest.
Police are asking anyone with any information about the vandalism Kirwans Hut to call them on 105; or go online to 105.police.govt.nz citing case file number: 240116/7979.
- Brendon McMahon, Local Democracy reporter