In the present study, PHB a biopolymer produced by Bacillus spp was evaluated against coccidiosis. PHB production by Bacillus spp was screened by Sudan Black staining and confirmed by Nile Red staining. The produced PHB was characterized by FTIR, NMR and XRD analysis. The characterized PHB was further used to evaluate its effect against sporulation inhibition and cell wall integrity of E.tenella oocyst. PHB at different doses (10, 20, 50 and 100mg) were used for sporulation inhibition studies. Potassium dichromate (2.5%) and oocyst suspension were used as positive and negative control. The sporulated and unsporulated oocyst were counted at 0, 24 and 48 hrs interval and sporulation inhibition percentage was calculated. PHB at the dose rate of 100mg (62.40%) has highest effect on inhibiting the sporulation of E.tenella oocysts when compared to other doses of PHB 50mg (53.33%), 20mg (45.42%), 10mg (46.20%) and positive control group (8.60%) at 24 hours. At 48 hrs, PHB at the dose rate of 100mg (31.70%) showed highest inhibition effect when compared to other doses of PHB 50mg (25.65%), 20mg (19%), 10mg (13.90%) and positive control group (8.60%). At the dose rate of 100mg of PHB, breakage was noticed at the outer proteinaceous wall of E.tenella oocyst.