Excess ammonia-nitrogen (ammonia-N) in the aquaculture environment destroys the shrimp excretory systemand osmotic balance; thus, affecting health and growth. The behavioral responses that often accompany internalphysiological changes are a reaction to environmental stress. Therefore, behavioral observations combined withphysiological measurements provide a more complete understanding of the homeostatic perturbations of shrimp fromexternal or internal stressors. The effects of ammonia-N on growth, body composition, and immunity of shrimp havebeen studied extensively, but the effects on locomotor behavior and energy allocation are not known. We investigatedthe effects of ammonia-N on locomotor behavior and energy metabolism of Litopenaeus vannamei, a commerciallyimportant shrimp species, to provide useful information for shrimp health and regulation of the aquaculture environment.Shrimp (weight, 4.89  0.27 g) were exposed to four ammonia-N concentrations of 0.02 (control), 1.00, 2.50, and5.00 mg/L in aquaria for 2 weeks at a water temperature of (28  0.5) ℃. The locomotor behaviors of L. vannamei wererecorded by cameras, and energy budgets were determined. Video of each aquarium was recorded for 30 min at 8: 00,12: 00, and 16: 00 during the daytime and at 21: 00, 24: 00, and 3: 00 during the night and analyzed to calculate movementfrequency and locomotion distance of shrimp in each experimental group. Feeding, growth, body composition,and defecation were measured to calculate energy budgets. The results showed that frequency of movement and locomotiondistance increased initially and then decreased during the day, but decreased at night as ammonia-N concentrationincreased. Movement frequency and locomotion distance of shrimp in the 5.00 mg/L ammonia-N concentrationwere significantly lower than those of the controls, regardless of time (P < 0.05). Specific growth rate, feeding rate, andfood conversion efficiency of L. vannamei decreased significantly as ammonia-N concentration increased, and allshrimp exposed to ammonia-N had significantly lower values for these variables than those of the control (P < 0.05).Crude lipid and energy contents in shrimp exposed to 2.50 mg/L and 5.00 mg/L ammonia-N were significantly higherthan those of the controls (P < 0.05). Less energy was allocated to growth as ammonia-N concentration increased,whereas that for metabolism increased. Energy for growth in shrimp exposed to 1.00, 2.50, and 5.00 mg/L ammonia-Ndropped 2.48%, 2.19%, and 4.57%, respectively, whereas that for metabolism rose 1.32%, 1.69%, and 5.70%, respectively,compared with the controls. These findings indicate that L. vannamei reduced food intake under ammonia-Nstress, decreased locomotor behavior to adjust energy allocation to reduce energy consumption, and allocated more energyto basic physiological metabolism, resulting in decreased energy utilization efficiency and inhibited growth. Thisstudy provides a mechanism for energy allocation in L. vannamei under ammonia-N stress and shows the behavioralresponses of the shrimp to ammonia-N stress, which will contribute to producing healthy shrimp and monitoring waterquality using animal behavior.