Trichomoniasis in birds is one of the most common types of infection that affects birds worldwide, and it is caused by Trichomonas gallinae. This study was carried out to examine and determine the presence of T. gallinae in Columba livia, Streptopelia turtur, and Gallus gallus domesticus microscopic examination (direct smear and Giemsa stained). The study was conducted in Balad district in Salah al-Din Governorate, north of Baghdad, Iraq, from October 2021 to March 2022. The results showed the microscopic examination that the incidence of T. gallinae average was 19.17%, distributed between 14.16% for C. livia, while S. turtur constituted 14.0%, and the rate of G. gallus domesticus was 27.92%, but there were no significant differences at P> 0.05 among these bird species. The gender of birds showed that there were no differences between a male and a female of each type. In males of the two types of pigeons (C. livia, and S. turtur) and Gallus gallus domesticus, the rates of infection were (16.10, 15.05, and 5.75 %), while in female types of C. livia, S. turtur, and Gallus gallus domesticus, the rates of infection were (12.17, 12.28, and 31.11%), respectively. The incidence of T.gallinae is distributed for the most studied months, as it showed the highest infection rate for pigeons in January at 20% for C. livia, and 32% for S. turtur, and while January to February had 33% as the highest rate of infection in G.gallus domesticus, although there were no significant differences (P>0.05) among studied birds. The histological changes of infected organs for all species as well as for healthy birds, as the parasite was located in the upper part of the gastrointestinal tract, which was tongue, pharynx, vesicle, and gizzard. Granular lesions and infiltration of lymphoid and inflammatory cells were found, as well as degeneration in a number of gland-forming cells. The mucous in the affected areas as a result of parasite penetration into the tissue, congestion of blood vessels and appearance of granulation tissue in the upper part of healthy alimentary canal was compared with that of C. livia, S. turtur and Gallus gallus domesticus of Balad distract. In pharynx, the infiltration of large numbers of white blood cells, scattered and nodular form, and the sloughing of surface cells, and presence of strands of sloughed keratin appeared in pharynx cavity, and in vesicle tissue, and in gizzard, the histological sections showed the presence of parasite in muscle layer surrounded by a white transparent band, the infiltration of a large number of white blood cells appeared, and degeneration of epithelial cells at the bases of epithelial cells appeared in mucous folds.