Eimeria tenella is one of the most important species of Eimeria that infect domestic fowl, causing coccidiosis in the poultry industry associated with drastic economic loss. Alternative treatment options are often necessary since anticoccidial drugs are prohibitively expensive, have serious side effects, or develop resistance. The role that herbal medicine plays in basic healthcare has been rediscovered worldwide. Consequently, our research assessed the in vitro inhibitory effect of escalated concentrations (6.25 mg, 12.5 mg, 25 mg, 50 mg, and 100 mg/ml) of Acacia nilotica aqueous extract (ANAE) on Eimeria tenella sporulation. Statistical analysis revealed that ANAE decreased the percentage of oocyst sporulation in a dose-dependent manner. Furthermore, ANAE showed abnormal sporulation and morphological deterioration of E. tenella oocytes. Area Under the Curve (AUC) calculation was used to determine the efficacy of ANAE and revealed that ANAE concentrations significantly reduced the coccidial score index. At 100 mg/ml, ANAE completely suppressed the sporulation of E. tenella oocysts, with obvious changes to their morphology and size. The phytochemical analysis of ANAE has shown that ANAE contains several active principles that possess anthelmintic activities. These compounds include tannins, saponins, flavonoids, terpenoids, and alkaloids, which can be attributed to the anticoccidial activity of ANAE. Considering our findings, we recommend that ANAE be used to prevent and control Eimeria.