The results of a toxicology report showed Geldof, 25, who died suddenly on April 7, had the drug in her system.
Geldof was the second daughter of musician and campaigner Bob Geldof and the late Paula Yates, who died of a heroin overdose at the age of 41.
At a brief inquest in Gravesend, Detective Chief Inspector Paul Fotheringham , said, "Recent use of heroin and the levels identified were likely to have played a role in her death."
Initial autopsy and toxicology reports were inconclusive.
"At this stage, the death is being treated as an unexplained sudden death. Officers are working to establish the circumstances around the death," Kent cops said at the time of Peaches's death.
Prior to her passing, the star became "increasingly obsessed" with the death of her mother. Back in 2000, Yates died of heroin overdose while she was alone with Peaches's then-4-year-old sister Tiger Lily.
Peaches was survived by husband Thomas Cohen and two sons, 2-year-old Astala and 1-year-old Phaedra.
Geldof - married to 23-year-old Cohen, a musician - wrote for British magazines and newspapers and presented celebrity-driven television shows.
The inquest heard that the last person to see Geldof alive was Cohen's father Keith, who dropped off Phaedra with her the night before.
He husband became alarmed the next morning when he could not contact her and drove to the house with his mother, only to find Geldof dead.
Phaedra was found nearby unharmed.
The inquest was adjourned for a full hearing on July 23.
Bob Geldof identified his daughter's body, the inquest heard.