Johnson-Koulianos was released from Johnson County Jail after posting $8,000 bail Tuesday. The 23-year-old was expected to make a court appearance Wednesday on charges including possession of controlled substances, keeping a drug house and unlawful possession of a prescription drug.
Ferentz says in a statement that he's "highly disappointed to learn of the charges."
Court documents say Johnson-Koulianos was arrested after officers executed a search warrant at his home. Police say investigators found more than $3,000 in cash, marijuana, cocaine and prescription drugs.
Johnson-Koulianos of Campbell, Ohio, caught 46 passes for 745 yards and 10 TDs this season. Jail officials didn't immediately know if he had an attorney Tuesday night and a telephone listing could not be found for his home address.
Johnson-Koulianos is Iowa's career leader in receptions and receiving yardage, and was named first-team all-Big Ten this year.
Information from The Associated Press was used in this report.