Officers attended the flat on Nottingham Road, Somercotes, at 4.10am.
A police spokesman said: “On arrival a 26-year-old man was found to be having a cardiac arrest and a short time later died at the scene.
“He is thought to have died of a suspected drugs overdose.”
Enquiries are at an early stage.
Anyone with information is asked to call Derbyshire police on 101 quoting incident number 111 of May 14.
Information can also be passed anonymously via Crimestoppers on 0800 555 111.