On Friday, Prime Minister 'Akilisi Pohiva commissioned the station, which will analyse sea level rise to improve coastal planning and preparedness.
The station was funded by Australia and installed in June.
It is one of 14 such stations in the Pacific Sea Level Monitoring network.
The Australian High Commissioner Andrew Ford said it would improve understandings of the impact of climate change.
The director of the Tonga Meteorological Service 'Ofa Fa'anunu said the station would also assist with the Pacific's tsunami monitoring network.
