Conus diminutus is a species of sea snail, a marine gastropod mollusk in the family Conidae, the cone snails and their allies.
Like all species within the genus Conus, these snails are predatory and venomous. They are capable of "stinging" humans, therefore live ones should be handled carefully or not at all.
The size of the shell varies between 9 mm and 22 mm.
This species occurs in the Atlantic Ocean along the west coast of the island Boa Vista, Cape Verde.