Two workers in the store told police that the man threatened them before taking some money and leaving.

No one was hurt during the robbery.

Police established a crime scene at the pharmacy and searched the area for anyone matching the man's description.

He was described as being about 183cm tall, with an athletic build and wearing a white hard hat, black sunglasses, a balaclava, a fluorescent jacket, blue pants and dark-coloured black boots.

Anyone with any information is urged to contact Blacktown police on 9671 9199 or Crime Stoppers on 1800 333 000.