The installations were carried out by using the Neptune jack up vessel owned by Geosea.
Atlantis said: “All four foundations have now been successfully installed using the Neptune jack-up vessel which has been demobilised from the project site.”
“This offshore operation was a resounding success and importantly has validated the use of jack up vessels for the purpose of installing tidal turbine foundations offshore in high flow locations.”
The company said that the use of a jack-up rig for the installations offers a flexible and fast installation solution for the tidal power industry.
The project is expected to generate first power by the end of the year.
It is being developed in two phases in the Inner Sound of the Pentland Firth, between mainland Scotland and Orkney.
In June, Atlantis connected the MeyGen tidal stream energy project to the 33kV Ness of Quoys distribution network in Scotland.
The project is also planned to be connected with high voltage transmission network, which is managed by Scottish Hydro Electric Transmission (SHETL).
Upon commissioning in the second half of this year, the project is expected to generate clean electricity enough to power 175,000 households in Scotland.
