The incident took place in Muthoot Finance in Rohini around noon.
The robbers entered the office disguised as customers and overpowered the employees at gunpoint, a senior police official said.
Police said the robbers fled with Rs 1.35 lakh in cash and some gold jewellery, the cost of which is yet to be ascertained.
The security guard Rajesh Mishra tried to catch the robbers but was stabbed. He suffered minor injuries, police said.
A case regarding the incident has been registered.
Investigators are scrutinizing CCTV camera footage and probing the case from all angles.
