The worker was reported missing about 4am local time after his colleagues could not make communications contact with him and entered the area he was working in, about 20 minutes descent underground.
The three men found a section of earth collapsed and after being unable to locate their colleague, they went back to the surface and raised the alarm.
As of 3pm local time, search crews had returned to the surface after using a thermal imaging drone and a robotic camera to investigate the collapsed area.
"They are currently reviewing the footage from the scene and have not yet located the man or identified signs of life," a statement from Tasmania Police said.
The mine is owned and operated by Pybar Mining Services subsidiary Diversified Minerals.
"Our immediate priority is to ensure the welfare of the person not accounted for, and the safety of those involved in the rescue," Pybar CEO Brendan Rouse said.
"Pybar are working closely with the Henty site team to establish the extent of the affected area. We are doing everything possible to ensure we access the area as safely and quickly as possible."
Henty has been suspended while the rescue effort is in progress.