Tryptophan (TRP) and vitamin E (VITE) modulate the stress response in animals, so they may also induce changes in behavior. The goal of the study was to determine the effect of high TRP and VITE diets on steers behavior. Angus steers were used in 2 experiments (E1 and E2), with a 21-d washout period in-between. Steers were distributed in pairs in 16 pens and fed the experimental diets for 5 d before a stressful event (45 min in a single file chute for E1 and slaughter for E2). Diets were designed in a factorial arrangement, with TRP at 0 and 100 mg·kg BW⁻¹·d⁻¹ and VITE at 0 and 2000 IU·hd⁻¹·d⁻¹ (n = 4 pens). Steers were randomly assigned to diets in E1, and E1 diet was used as blocking factor for randomization in E2. Video cameras were used to record 24 h·d⁻¹ during supplementation, and also one day after stress in E1. Behavior was evaluated at d 2, 4, 5 and 6 of starting supplementation in E1, and at d −1, 0, 2 and 4 in E2. Behavior was observed every 10 min and compared as proportion of observations where animals were in standing or lying posture; and doing one of the following activities: defecating, drinking, eating, interacting, no detectable activity, ruminating, self-grooming, and stereotypic movements (bar licking, tongue rolling, etc.). Statistical analysis was made using repeated measures, with TRP, VITE, time and their interaction in the model. In E2, diet in E1 was used as blocking factor and d −1 was used as covariate. When ANOVA P < 0.1 for TRP, VITE or TRP × VITE, comparisons with control were made using Dunnett adjustment. When ANOVA P < 0.1 for any interaction with time, comparisosns were made within day. In E1, none of the diets including TRP or VITE was different to the control in any variables. In E2, animals receiving TRP tended to spend a higher proportion of their time eating (P = 0.091), while animals receiving VITE tended to spend a smaller part (P = 0.076) than their controls. Animals receiving TRP and TRP+VITE presented less stereotypic movements (P = 0.008 and 0.017, respectively) than their controls, and animals receiving VITE spent a smaller proportion of their time interacting (P = 0.032). We concluded that TRP and VITE produced small changes in behavior in steers and no changes the day after a stressful event.