The poultry sector is facing multiple challenges among which infectious diseases are major hindrances. Coccidiosis, especially cecal coccidiosis is the most prominent disease because of its acute nature and high mortality. Controlling through synthetic chemicals and ionophores is becoming less effective, botanicals especially essential oils are being considered for the control of coccidiosis. In this study, broiler birds at day 10 of age were divided into 6 groups. Three concentrations of flaxseed (Linum usitatissimum) essential oil 1, 2 and 3% (v/w) were administered orally to estimate their anticoccidial effects compared to toltrazuril medicated, infected non-medicated, and non-infected non-medicated controls. Oocysts per gram of feces, oocyst score, fecal score, lesion score, feed conversion ratio, weight gain, complete blood profile, and liver and renal function-related serum parameters were evaluated. Analysis of variance and Tukey’s post hoc test were used to compare the means and analyze statistically. The results showed that flaxseed essential oil had significant (p<0.05) anticoccidial activity in reducing oocysts per gram, oocyst score, fecal score, and lesion score. There was a significant decrease in mortalities, while weight gain and FCR were also improved by therapy of flaxseed essential oil at a concentration of 3%. Flaxseed essential oil also showed significant positive effects on red blood cell counts, packed cell volume, mean corpuscular hemoglobin, and hemoglobin concentration. Total proteins and albumins were significantly (p<0.05) increased by the flaxseed essential oil while other serum-related parameters remained in the normal range. The results suggest that the flaxseed essential oil can be used for the control of coccidiosis in broiler birds.