Opuntia tomentosa is endemic to Mexico, where it is widespread in the Mexico Federal District and the states of Aguascalientes, Guanajuato, Guerrero, Hidalgo, México State, Michoacán, Morelos, Nuevo León, Oaxaca, Puebla, Querétaro, San Luis Potosí, Tamaulipas, Tlaxcala, and Veracruz (and Jalisco?) and Guatemala. It is adventive in Australia, South Africa and elsewhere as a minor rangeland pest.Altitude range: It grows from 1,090 to 2,600 metres above sea level.Habitat and Ecology: This species is mostly found in sub-tropical, semi-arid and warmer temperate environments. In Mexico it inhabits Quercus forests, xerophyllous scrub and grasslands in a volcanic area on shallow soils, and tolerates disturbance. Climate is semi-arid and modified by altitude, however water availability is highly restricted due to a great percolation caused by the rock structure and to low water retention from the shallow accumulated soil and also a daily wide temperature fluctuation could occur (as wide as ~ 34°C).