Police said the robbers used hammers to break glass display cases at Z Fine Jewelry in Hawthorn Mall after it opened for business.
One suspect threatened an employee with a hammer when they called 911, police said.
The two suspects were last seen wearing dark hoodies and black masks driving towards Milwaukee Avenue in a dark SUV, police said.
Police said it's unclear how much jewelry was taken. The store is now closed while police investigate.
No one was hurt in the incident. Vernon Hills police are asking anyone with information about the robbery to contact the investigations department at 847-918-5601.