Origin and Habitat: Mammillaria mammillaris is found in the coast of Venezuela and and the adjacent islands Antigua and Barbuda; Aruba; Bonaire, Sint Eustatius and Saba (Saba, Sint Eustatius); Curaçao; Dominica; Grenada; Guadeloupe; Martinique; Montserrat; Saint Kitts and Nevis; Saint Lucia; Saint Martin (French part); Saint Vincent and the Grenadines; Sint Maarten (Dutch part); Trinidad and Tobago. It is a common species with a widespread distribution and abundant populations especially in Venezuela.
Habitat: It is found in costal and mountainous regions at medium altitude (up to 1.500 m) in clearings in spiny scrublands and thorny forests and do not tolerate frost. It also occurs on offshore rocky islands. Part of its habitat is being converted for agricultural activities such as crop production. It is unknown whether collecting from the wild (for ornamental plants) is affecting the population status since this species is relatively common.