The Eco Festival will take place in Lower Castle Park between 11am and 6pm on September 2.
It will act as an educational platform teaching visitors about energy, transport, waste reduction and upcycling.
Throughout the day, there will be crafts sessions for children and activities such as yoga, pilates and dance classes to join.
In addition to talks there will be bands and acts like Fraser Morgan, Elmer & Friends, the Cloë Lupton Band and Susy Cramer.