In 1923, after helping design its new Aquarium, Procter joined ZSL's staff as Curator of Reptiles and Amphibians at London Zoo.
Following approximately four months of work on the design of the new Aquarium, Joan Procter formally joined the staff of the Zoological Society of London (ZSL) in 1923 as Curator of Reptiles and Amphibians at London Zoo. This appointment marked her transition from museum research into the highly visible world of public zoological institutions, where she would spend the remainder of her career.
In this role, Procter had direct responsibility for the care, breeding, and public display of the zoo's reptile and amphibian collections, one of the largest and most important in the world at the time. She quickly became known for her innovative approaches to enclosure design, prioritizing conditions that mimicked animals' natural habitats and behaviors—principles that were ahead of their time in zoo management and animal welfare.
Her appointment to such a senior and specialized curatorial position was a landmark achievement, given how few women held comparable posts in major scientific or zoological institutions in the early 1920s. Procter used her position to advance both public education and scientific research, famously working closely with Komodo dragons brought to the zoo and becoming an internationally recognized authority on reptile care. Her tenure fundamentally reshaped how reptiles were exhibited and studied in captivity, leaving a legacy that influenced zoo design and herpetological curation for decades after her death.