Police investigating an armed robbery at a north-western Sydney convenience store are appealing for public assistance.

Two teenage boys entered the store on Bank Street at Meadowbank about 6.30pm yesterday (Sunday 22 May) and demanded cash from the 56-year-old female owner.

One of the teenagers then produced a knife before they left with a sum of cash. They were last seen walking on Meadow Crescent.

The store owner was uninjured.

She has described the two youths as being Caucasian in appearance, about 170cm tall and aged between 15 and 17 years old. They were both wearing dark clothing.

Officers now want to speak to anyone with information about the robbery and urge them to call Gladesville Police via Crime Stoppers on 1800 333 000.