An estimated £9,000 worth of stock was taken from a retail unit owned by Fenside Outdoors Ltd on the Gymphlex car park in Boston Road.
The theft apparently took place last night (Thursday) and police are investigating.
Items stolen are mainly country clothing, boots and jackets. They include brands by Champion, Cabotswood, Sherwood Forest, Harvey Parker and Lansdown.
A staff member said: “As a small family business, this is devastating to us.”
• Anyone with information can contact police on 101, quoting incident number 65 of February 24.