Thrips (Thysanoptera: Thripidae) are the major insect pest of seedling cotton, Gossypium hirsutum L., on the Texas South Plains. The western flower thrips, Frankliniella occidentalis Pergande (Thysanoptera: Thripidae), has historically been the most abundant thrips species in cotton in the region. A field survey during the 2017 and 2018 growing seasons collected thrips from small-plot insecticide seed treatment research experiments at multiple locations across the Texas South Plains. Species composition of adult thrips from cotyledon to four true-leaf stages cotton was determined by morphological identification with the aid of a microscope. Of the species collected during 2 years of study, 64% were onion thrips, Thrips tabaci Lindeman, followed by F. occidentalis (23%), Frankliniella exigua Hood (10%), and tobacco thrips, Frankliniella fusca Hinds (1%). Relative abundance of species varied significantly across growing seasons. In 2017, T. tabaci was the most abundant species in cotyledon to four true-leaf stages of cotton. In 2018, F. occidentalis was more prevalent than other thrips species. The percentage of adults was significantly greater than that of immatures at the cotyledon stage while immature thrips were significantly more abundant during one to four true-leaf stages of cotton. The study indicated T. tabaci and F. occidentalis were the most prevalent thrips species on seedling cotton on the South Plains of Texas.