Very little is known about the Mexican fauna of Uroleucon; only 4 species have been recorded, which is fewer than in Central America and the Caribbean. One hundred ninety two samples collected in 19 Mexican states from the Muséum national d'Histoire naturelle (Paris) collection have been studied and 30 species identified. Four of them are the species previously recorded (U. ambrosiae, U. erigeronense, U. pseudoambrosiae and U. sonchi). Fifteen North American species are recorded for the first time from Mexico: U. astronomus, U. brevitarsus, U. chani, U. eupatoricolens, U. gravicorne, U. macgillivrayae, U. maximilianicola, U. nigrotuberculatum, U. obscuricaudatum, U. paucosensoriatum, U. penderum, U. reynoldense, U. richardsi, U. stoetzelae and U. zerogutierrezis. Thirty-three new “aphid/host plant” relationships of these species have been established. Comments about the distribution of the species are made. Eleven new species are described, illustrated and discussed: U. penae, U. mexicanum, U. gnaphalii, U. sinuense, U. munozae, U. zacatecense, U. queretarense, U. tlaxcalense, U. latgei, U. heterothecae and U. remaudiereorum. An appendix with modifications for 17 keys in Blackman and Eastop's work, “Aphids on the World's Herbaceous Plants and Shrubs”, is presented and 3 additional keys are given.