Officers swooped on properties in Ropery Street and Abbey Way earlier today (Tuesday) and executed warrants under the Misuse of Drugs Act.
Almost £7,000 in cash and some 10,000 tablets, believed to be steroids, were seized during the raids.
A quantity of other drugs were also confiscated during the operations, which were carried out simultaneously.
Humberside Police said a man has been arrested on suspicion of being concerned in the supply of controlled drugs and money laundering.
He is currently in police custody.