The robbery, at Carlisle Newsbooze, in Carlisle Street, happened at about 4.15pm on Saturday.
A man walked into the shop and threatened a member of staff.
Humberside Police said the offender then stole cigarettes and a "significant" amount of cash from the newsagents.
He left the shop and fled towards Hook Road, riding a yellow bicycle which had a basket on the front.
The offender also had his face covered with possibly a scarf, and was wearing a dark coat, with a fur trim around the hood and blue jeans.
Anyone with information is asked to call police on 101, quoting log 387 of March 24.