Work is due to begin on the Bishop's Palace Gardens project next month. The design is by Sue Sutherland Landscape Architects.
Funded by Chichester District Council, it will include new planting, improved access and the creation of a wildlife-friendly area.
Over the past three years the Friends of Bishop's Palace Gardens have worked closely with the council to develop the project.
The new-look Bishop's Palace Gardens, complete with water features and a pergola walk, will be officially opened in spring next year.
The final phase of the project will involve planting hundreds of shrubs, trees, roses, climbers and herbaceous plants. This work will be undertaken by the Friends of Bishop's Palace Gardens and the council's parks team.
Scandor Landscape Contractors will carry out work on the project.