Deadly Secret may refer to:
Book A Deadly Secret, a 1963 wuxia novel Deadly Secrets: The CIA-Mafia War Against Castro & the Assassination of J.F.K., a 1981 non-fiction book by William W. Turner and Warren Hinckle A Deadly Secret: The Strange Disappearance of Kathie Durst, a 2003 book about Robert Durst
Film and television A Deadly Secret (film), a 1980 Hong Kong film Deadly Secret, a 1989 Hong Kong television series