Curtis, 66, signed a letter to Sally Bolton – chief executive of the All England Lawn Tennis Club (AELTC) – objecting to the bank on climate change grounds ahead of the event kicking off on Monday.
At the tournament on Sunday, he wore a dark suit with a light blue tie and could be seen chatting to former Pointless co-presenter Richard Osman in the box.
Other signatories to the letter included Dame Emma Thompson, musician Brian Eno, Green MP Caroline Lucas, Dragons’ Den star Deborah Meaden and retail consultant and broadcaster Mary Portas.
The campaigners wrote: “Barclays is financing and profiting from climate chaos, and accepting a sponsorship deal from them is an endorsement of these actions.”
Wimbledon announced Barclays as its official banking partner in November as the bank took over from HSBC.
The signatories also said Wimbledon’s partnership was not “consistent” with the Grand Slam event’s environmental policies.
The letter also stated: “We hope you will reconsider this decision, and end your partnership with Barclays.
“In taking such action, you can show real climate leadership, and maintain the AELTC’s proud position of cultural and sporting leadership, both in the UK and across the world.”