Haemogregarines are haemoparasites (Apicomplexa: Adeleiorina) of all class of vertebrates nearly, worldwide. The present study was aimed to establish and describe the developmental stages of a Haemogregarina species infecting Nile monitor (Varanus niloticus). The captured Nile monitors were three animals with 80-100 cm in length, they captured from Qena province, Southern Egypt, and thin blood films were prepared and microscopically examined. Also, small pieces of the liver and the lungs of the infected animals were separated and prepared for sectioning, which stained and examined. The recovered parasites have rod-like bodies, infecting the erythrocytes only, with a single stage, in a parasitophorous vacuole and have no karyolitic effect. The parasitaemia level was found up to 50\10,000 counted erythrocytes. Only gamonts have been recognized in blood smears, and they were found in two forms; the first form is short, thick (called short gamont) and measured 11.02 × 2.65 µm. The second form was found long and thin (called long gamont), with a subterminal nucleus, measured 14.18 × 2.45 µm. Both forms cause either slightly or strong displacement of the host cell nucleus. The infected erythrocytes had either slightly or markedly hypertrophied in presence of short and long gamonts. The infected erythrocyte measured 18.05 × 8.87 µm, but the uninfected erythrocyte was 16.52 × 8.77 µm in length and width, respectively. Schizogony phase was observed in the lungs only of the infected Nile monitor, where the meronts were formed within parasitophorous vacuoles. The parasite nucleus divided many times, and the produced nuclei are peripherally arranged in the meront, forming merozoites. After separation of the merozoites, residual bodies formed. The merogonic stages were differentiated into two forms, micromeront that measured 15.57×14.29 µm, and produces a few numbers of macromerozoites, meanwhile the macromeront measured 19×15.9 µm and produces up to six micromerozoites.