An official ceremony is being held to celebrate the opening of Ysgol Bro Dinefwr at Ffairfach, Llandeilo.
It will take place on the morning of Tuesday, October 4, with a programme of events including the unveiling of a plaque.
Pupils will welcome guests to the ceremony and perform musical items; dignitaries including county council Leader Cllr Emlyn Dole, education Executive Board Member Cllr Gareth Jones and Chair of Governors David Dyer will give addresses.
Cllr Dole will also unveil a slate plaque to commemorate the occasion, and Rev Ian Aveson, Vicar of Llandovery, and Rev Michael Sadler, Vicar of Llandeilo, will give blessings.
The opening of the new £30million school, which is being sponsored by contractors Bouygues UK, includes the presentation of a ceremonial key and a Secure by Design certificate.
Headteacher Julie Griffiths will compere the proceedings and give a speech, plus a short tour of the new school.
Bro Dinefwr caters for 1,200 pupils in the area, including a 200 pupil sixth form and 30 place specialist provision for children with additional learning needs.
The category 2B bilingual school was delivered in partnership with the Welsh Government through its 21st Century Schools programme.
It provides first class accommodation and facilities, plus high quality vocational courses with other Dinefwr schools and Coleg Sir Gar.
Cllr Jones said: “We’re very much looking forward to this official opening, pupils have occupied their new building since September and they have settled in very well.
“This is a state of the art school which is what we are aiming to deliver for all pupils in Carmarthenshire.”
Ysgol Bro Dinefwr was part of an overall investment of around £70million in schools in the Dinefwr area.