As a long-time supporter of the animal charity, the prince was just 13 years old when he first showed his enthusiasm by joining the ZSL's Exceptional Young Zoologist Club.
Now the first-in-line to the throne, 65, has cemented his passion and joins his mother the Queen as a representative for ZSL. The Queen has been the royal patron of the society since her coronation in 1953.
Director general Ralph Armond said that he was "delighted" that Charles would be taking up the five-year term. The royal will be involved in a range of work, which includes ZSL London Zoo and ZSL Whipsnade Zoo, conservation projects in more than 50 countries around the world, and the society's research arm, the Institute of Zoology.
Charles paid a visit to the London Zoo last year, accompanied by his equally keen eldest son Prince William, which Ralph mentioned in his statement.
"During the Prince's recent visit in November it was clearly evident that he shares our passion for animals and protecting them in the wild," said Ralph.
The royal duo were given a tour of the new tiger exhibit where they came face to face with a male Sumatran tiger, Jae Jae. Charles and William then met with conservationists to discuss how to end the illegal wildlife trade.
The father and son team recently fronted a week-long campaign to fight the illegal trade back in February. Their aim was to raise awareness about the trade — which sees elephants, rhinos, tigers and other endangered animals facing near extinction — and to come up with solutions such as reducing consumer demand and enforcing tougher laws.
"The Prince's commitment to stopping illegal wildlife trade is very closely aligned with ZSL's conservation work," added Ralph. "He has shown particular interest in the conservation technology we are developing, including next-generation cameras that will be used by park rangers to help catch poachers."