An elderly couple needed medical treatment after being attacked in their home near Stow-on-the-Wold during a robbery on Friday.
Three men talked their way into the house at Bledington around 1700 BST by claiming they were from a water company.
It is believed the couple, in their 80s, were assaulted before the robbers escaped with a substantial amount of cash.
The pensioners were left locked in the house.
A police spokesperson said: "This is a very serious robbery that has left the couple traumatised and shaken."
It is thought the men escaped in a car waiting outside.
All men were white, between 5 ft 7 ins and 5 ft 10 ins tall and of varying builds.
Police are appealing for witnesses.