It happened on January 30 at the Bottoms Up Night Club on the 4600 block of North 5th Street.
Police say the 42 year-old female victim was just finishing her shift at the club around 2 a.m. when the suspect approached her from behind and placed an unknown object to her back.
The robber then forced her to open the cash register.
As the suspect was grabbing the money, the employee was able to flee the club and call police.
There were no injuries reported during the robbery.
Police describe the suspect as a light complected black or Hispanic male, 5'8 tall and 175lbs. with facial hair. He was wearing a light colored hooded sweatshirt, black knit hat, black pants and black gloves.
Anyone with information is asked to contact police at 215.686.TIPS (8477) or text a tip to PPD TIP (773847).