The BBC says the Liverpool-born Sladen died from cancer on April 18.
Sladen joined the broadcaster in 1973 as Doctor Who's assistant Sarah Jane Smith, opposite Jon Pertwee and Tom Baker.
Sladen went on to star in spin-off The Sarah Jane Adventures, four series of which were carried on the BBC's children's channel, CBBC.
The BBC said in a statement on Tuesday that Sladen was survived by her husband, actor Brian Miller, and her daughter, Sadie.
Funeral arrangements were not immediately available.