The Queen's daughter unveiled the new Lucky Pup dog-friendly cafe - an expansion of a previous venture that now has seating for 150 people.
The menu includes canine treats and the project has been three years in the making after owners the Nicholson family realised their smaller dog cafe had outgrown its building.
The cafe is outside the main farm complex and aimed at dog walkers who are not required to pay the Cannon Hall admission fee.
Princess Anne was given a tour of the site by Robert Nicholson and heard about the farm's Facebook Live broadcasts and animal adoption scheme.
Mr Nicholson said: "It has been some years in development and has faced a few bumps along the way but we are thrilled to reveal our 150-seat brand new dog cafe has now been officially opened by Her Royal Highness - who took a break from her duties for a spot of afternoon tea with Roger and Cynthia, the founders of the attraction.
“It was a real honour to show Her Royal Highness our family farm and she seemed genuinely interested in what we had to say. She was here quite a few hours and it was a wonderful tribute to the hard work of our staff who have really pulled together to keep the business going throughout lockdown."