The Daily Mail says Dickov is a free agent following his release by Leicester City last month and has already been training with the Elland Road club.
Leeds, though, had to get special dispensation from the FA in order for 37-year-old to join.
FIFA rules prevent players appearing for more than two clubs in the same country in one season, and Dickov has already appeared for Leicester and Derby County.
Boss Simon Grayson said: "His experience is phenomenal and he's a fiery little so-and-so. He can only add to the quality in our dressing room."