The store in City Walk will be open for one last day on Sunday, from 10am to 3.45pm.

There will be cake and, possibly, champagne to celebrate a place that has been less a retail store and more a meeting and "comfort place" for the past decade.

Its sister store, The Green Shed Underground, is slated to also close on May 25, but may have a last-minute reprieve, with ongoing negotiations between the owners of the building and the tenants.

Sandie Parkes and Charlie Bigg-Wither own both The Green Shed Shop and The Green Shed Undeground businesses.

They felt they had no choice but to close the city stores after The Green Shed did not win back its long-standing ACT Government contract to manage the reuseables depots at the Mugga Lane and Mitchell tips, from where the stock for the stores was sourced.

The St Vincent de Paul Society of Canberra/Goulburn won the contract to run the depots. It has nothing to do with the stores, but has promised all staff there will be a place for them at the society if they wish.

Robyn Campbell and Kaaron Warren have worked at The Green Shed Shop since it opened 10 years ago.

They have decided not to transfer to Vinnies but go back to their craft - Robyn as an artist and Kaaron as a writer.

Both felt strange to no longer be working at the shop come next week.

"I've never had a better job, never had better workmates," Kaaron said.

"Every day I come in, there's something else amazing to look at and somebody else amazing to talk to.

"So, I'm feeling a real loss of that."

Robyn said "there was also the thrill of the find".

"Every day was like a treasure a hunt," she said.

Both women said customers had been "devastated" by the closure and some had been in tears.

"We've actually got a book here to sign and the things that people are writing in there are so beautiful and heartwarming," Kaaron said.

"People have loved coming in here. It's a place of comfort, it's a friendly place. People have made friends in here. I'm not sure anyone has met the love of their life in here, but I wouldn't be surprised."

Robyn said some customers had been coming in every day for 10 years.

"It's that kind of relationship," she said.

"Because in this shop, everything turns over so quickly, every day there's new things, so every day they came in."

Both Kaaron and Robyn said The Green Shed Shop had also inspired their artistic works.

"I write horror and crime fiction so many of the objects that have come into the shop, have actually inspired stories," Kaaron said.

"I've found diaries, autograph books. I've been inspired by a cracked mug and you just wonder where it was before here."

Robyn is a sculptor and said she had learned so much from working in the shop.

"There's a hidden history in all these objects," she said.

"And people coming in with their own stories about the object is just so fascinating."

A spokesperson for the St Vincent de Paul Society Canberra/Goulburn said the transition was continuing as it was due to take over the Mitchell and Mugga Lane facilities from May 31.

"The transition arrangements are still being worked through with the ACT Government and the current operators," he said.

"A key part of this is making available opportunities for employment with those staff who wish to take this up and information sessions for them to meet and ask questions have been taking place.

"This is still a work in progress".