Tan Son Nhat Airport customs on Friday found a rifle, 50 bullets and two teargas shells in a consignment sent from the US.
They were hidden among clothes and personal items in a carton box, customs officers said.
The named recipient is a 27-year-old Vietnamese woman who was unable to produce relevant documents for the gun.
Customs officers are coordinating with police for further investigation.
Vietnam banned civilian ownership of air guns in 2006.