Stalls were placed in front of Andrea Welsher's craft shop Dragonflies in Ilkeston, Derbyshire, during a vintage vehicle event on Sunday.
She said stock was made specifically for the day but, because she could not open, she may now lose the business.
Organisers, the Erewash Partnership, said it "regretted" the incident.
A tearful Ms Welsher said she arrived at Dragonflies on Sunday to find stalls were blocking her entrance despite asking the organisers to avoid her shop front.
She said passers-by could not see the shop and it would have been a fire hazard to open.
"It's heartbreaking. I put my life and soul into this business and right now I don't know whether we have the funds to go forward through no fault of my own," she said.
"Erewash Partnership is supposed to help and support businesses... and they've left me with the possibility that we have to close."
No-one was available from the partnership but in an email to Ms Welsher, chief executive Ian Viles blamed private contractors.
"We very much regret that market stalls were erected in front of the Dragonflies shop on Sunday," he said.
"Although this did permit pedestrian passage to your shop door and windows, the situation was as unfortunate for you as it was unwanted by us."
A shopkeeper has said she may have to close for good after an event to promote small businesses prevented her from opening.