Out of eighty-nine marbled teals (Anas angustirostris) only thirty four birds were naturally infected with Eimeria sp. giving an infection rate of 38.2%. The oocysts of Eimeria sp. under experiment were subspherical to ovoid in shape with smooth, thin bilayered wall, 1 µm and measured 28.3 × 25.42 mm. Only one polar granule was observed. Micropyle and oocyst residuum was absent. Sporocysts were ovoid in shape and measured 14.5 × 10.5 µm. Each sporocyst had a stieda and substieda bodies. Sporozoites were elongated, granular in appearance and measured 7.1 × 3.8 mm. While, sporogony occurred through 4 days at room temperature forming four sporocysts, each sporocyst contains two sporozoites.