Police are urging Carlingford and North Rocks residents to be mindful of their home security following 10 recent break and enters in the area.
Officers allege the break-ins may be linked as they are all happening in daylight hours with similar signs of forced entry.
The suspect is believed to target older-style homes and ring the doorbell to check if the occupants are home before forcing a rear door or window open .
He is described as being of Asian appearance, 170cm in height, with a thin build and black hair.
Anyone who sees a man matching this description and acting suspiciously can ring Castle Hill Police, 9680 5399.
Police said the last break-in linked to the suspect was on January 23 in Arcadian Court, Carlingford.
During the break-in the thief forced open a rear window and stole cash and jewellery.
Police said residents should lock all entry points and place wood in window slats.