Brett will be responsible for Eden's 13ha outdoor space and the Mediterranean Biome. He replaces Tom Keay, who moved with his family to France in spring this year to develop a large garden.
Brett has been the glasshouse supervisor at Cambridge since 1999 following an eight-year period at the Royal Botanic Gardens, Kew. He has the Kew Diploma and a Master's degree in environment and development education.
Eden chairman of horticulture Don Murray said: "It's really exciting to be welcoming Rob to the Eden team. He's an inspirational educator, a strong leader and one of the most talented horticulturists in the UK. His appointment will mark a refreshing change for horticulture at Eden and will hopefully be the start of even greater things for us."