The work will be taking place at Newport Swimming Pool and Leisure Centre, with the venue closed from Monday, December 6.
Telford & Wrekin Council said that it is planned to reopen the gym by the end of March and the pool from the end of April.
The closure will allow for a range of what is described as "essential maintenance work" – which also ties in with the council's pledge to be carbon neutral by 2030.
The work involves the swimming pool tank, pool surround, water filtration and circulation, as well as improving the temperature control within the gym.
As part of the work, an air source heat pump will be installed and internal cladding added to the building.
The pool floor will also be remodelled to reduce the depth of the deep end and to try to increase the shallow water area.
In a statement the council said it would "make the pool more energy efficient, improve facilities and increase the capacity of the swimming lesson programme, whilst still allowing all existing activities to continue".
Councillor Eileen Callear, Telford & Wrekin Council's cabinet member for leisure, culture and visitor economy, said: “There is never a good time to have to close one of our leisure facilities to make improvements, but with time-sensitive external funding available from the carbon reduction grant we have taken the decision to carry out this vital work.
"It was not possible to carry out this work during the lockdowns. We apologise for the obvious inconvenience, however due to the nature of the work it is unfortunately essential. The facilities will close from Monday, December 6,with an anticipated reopening of the gym from the end of March and the pool from the end of April 2022. We hope that our regular users including aspirations members will understand the need for this temporary inconvenience."