Workers chased a robber's getaway vehicle after they saw him grab a cash box from a security guard.
The guard was targeted outside the Kirby and West dairy in King Richard III Road, near Leicester city centre shortly, after 1pm on Monday.
The crook managed to snatch the cash box from the guard, who was not injured, and began to run toward a waiting car.
A number of Kirby and West workers spotted the incident and chased after the robber, even after the car began to drive away.
At some point in the confusion the culprit dropped the security box as he and his accomplice fled.
All of the cash was recovered.
Kelvin Young, the dairy firm's general manager, said: "Some of our staff got involved when they saw what was happening to the security guard.
"They chased the vehicle but fortunately nobody was injured.
"It was adrenaline I suppose, they decided to have a go at helping this man."
A Leicestershire Police spokeswoman said: "A security guard was approached by a man who assaulted him and then stole a cash box.
"The suspect made off in a vehicle which was driven by another person.
"The guard was not injured during the incident
Contact Detective Constable Louise Rooke on 101 or Crimestoppers, which is anonymous, on 0800 555111.
