This study investigated behavioral activities (resting, moving, aggressive, social, and reproductive behavior) and fecal cortisol levels in 8 individually identified adult male blackbucks during periods of varying levels of zoo visitors (zero, low, high, and extremely high zoo visitor density). This study also elucidated whether zoo visitor density could disturb nonhuman animal welfare. This study analyzed fecal cortisol from the samples of blackbuck by radioimmunoassay and found significant differences (p < .05) for time the animals devoted to moving, resting, aggressive, reproductive, and social behavior on days with high and extremely high levels of zoo visitors. The ANOVA with Duncan's Multiple Range Test test showed that the fecal cortisol concentration was higher (p < .05) during the extremely high (137.30 ± 5.88 ng/g dry feces) and high (113.51 ± 3.70 ng/g dry feces) levels of zoo visitor density. The results of the study suggest that zoo visitor density affected behavior and adrenocortical secretion in Indian Blackbuck, and this may indicate an animal welfare problem.