The three men were working on the Wentworth Falls track when the rock slide occurred just before midday on Wednesday.
A worker suffering multiple fractures was winched from the scene and then transported by helicopter to Westmead Hospital in a serious condition.
The other patient remained on the scene at 3.30pm in a stable condition. He will also be flown out by helicopter.
It's not been officially confirmed if they were contractors or permanent National Parks and Wildlife Service staff.
Fifteen ambulances with a special team of paramedics and three ambulance helicopters are trying currently to help the injured at the site.
"Due to the remote location of the landslide it took rescuers some time to reach the site," police added in a statement.
SBS News understands the walking track has been closed due to dangers posed by falling rocks for some months.
The spectacular Wentworth Pass track was closed on Wednesday as the rescue operation continued.
A sign showing the track has been closed. Source: Supplied
The nearby National Pass track was closed in late August "due to a very dangerous, unstable section of rock above the walking track", the NPWS said at the time.
The area was assessed by a geotechnical engineer with measures then put in place to remove the "extreme hazard".
The track was due to be reopened in time for the December school holidays.
Due to the remote location of the landslide it took rescuers some time to reach the workers on Wednesday.
It's a 45-minute walk along the track to access the scene, an ambulance spokesman told radio 2GB.
Wentworth Falls received three millimetres of rain in the 24 hours to 9am, the Bureau of Meteorology reports, with more rain forecast for the rest of the day.
Fifteen ambulances, including special operations team paramedics, responded along with three rescue helicopters and NSW Police personnel.
Members of the public are being asked to avoid the area.
