Tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), is a damaging pest of cotton, Gossypium hirsutum L., grown in mid-southern U.S. states that include Arkansas, Louisiana, Mississippi, Missouri, and Tennessee. Chemical control tactics have been the primary method for managing infestations, but this strategy has become less effective due to development of insecticide-resistant populations. The objective of this study was to evaluate the efficacy of sulfoxaflor against a range of tarnished plant bug infestation levels compared to acephate, the most widely utilized insecticide. Across infestation levels (12 locations, 49 trials), sulfoxaflor applied at ≥ 50 g ai/ha provided control and yield levels similar to that observed with acephate. Against moderate infestations, single applications of sulfoxaflor (≥ 50 g ai/ha) or acephate reduced infestations below the action threshold 64 to 83% of the time through 8 d after application. Two applications of these same treatments and application timings against high infestations resulted in frequencies below the action threshold of 71 to 93%. Number of nymphs did not significantly differ between application of 50 and 75 g ai/ha of sulfoxaflor and acephate within single or sequential timings. As with any insecticide, effective tarnished plant bug control will depend on the quality of the application, pest population dynamics, and re-infestation intervals. Routine scouting practices will be necessary in determining the timing of insecticide treatments following a sulfoxaflor application. The new mode of action and efficacy provided by sulfoxaflor can be incorporated in cotton integrated pest management programs for tarnished plant bug that utilizes multiple insecticides.