Abstract The use of insecticide remains the frontline method in controlling red imported fire ant (Solenopsis invicta Buren) (Hymenoptera: Formicidae), one of the worst invasive ants in the world. Neonicotinoids are effective ingredients in toxic baits for suppressing S. invicta population. To search for new and effective insecticides, the toxicity and sublethal effects of triflumezopyrim, a novel neonicotinoid analog, were evaluated against S. invicta. No high mortality of ants was observed after they fed on sugar water containing 120 μg/ml triflumezopyrim for 72 h; however, 100% mortality was achieved after ants fed on sugar water containing 10 μg/ml triflumezopyrim for 2 wk. Furthermore, at 10 μg/ml, triflumezopyrim did not inhibit ant food consumption within the 7-d treatment period. These results indicate that triflumezopyrim is a slow acting toxin and may be qualified as bait toxin for managing red imported fire ants. At 1 μg/ml, triflumezopyrim did not cause any significant effect on colony growth within 56 d and did not inhibit the food consumption during the whole trial period. At 10 μg/ml, triflumezopyrim displayed a significant reduction of aggressiveness during confrontation with native ants, resulting in higher mortality than the ants in the control. However, at 1 μg/ml, triflumezopyrim did not show any significant impact on both aggressiveness and mortality of the red imported fire ants.