McAfee is indicted for fraud in the United States and spent time in jail on Tuesday pending his extradition after being arrested in Barcelona Airport.
The antivirus software pioneer was detained on Saturday as he boarded a flight to Istanbul with a British passport, a Spanish police source said.
A judicial source said McAfee was then presented to a high court judge through a video call and sent to prison without bail where he will await the extradition process.
A third source, from the Catalonia region's justice department, said he was in the Brians 1 jail, which opened in 1991 in an industrial area 45 minutes by car from Barcelona. Some local politicians have been jailed there for corruption.
After he was arrested, McAfee's official Instagram account posted a "Free McAfee" message with a photo of him.
The person running the account did not return a message seeking comment.
No other representatives were immediately contactable.