The offenders struck at Corby Garden Machinery in St James Road at some point between 6pm on Wednesday (June 14) and 9am the following morning.
They gained access to the property by cutting through a metal door and roof.
Once inside they stole power tools.
A police spokesman said: “Anyone with information can contact Northamptonshire Police on 101.
“Alternatively, they can call the independent charity Crimestoppers anonymously on 0800 555111.”