For today, the actual problem of veterinary medicine is the diagnosis of animal poisoning with organophosphorus pesticides, which are used as insecticides and acaricides, fungicides, herbicides, rodenticides, nematocides. One of the highly effective nonspecific organophosphorus insecticides is diazinon, falling into the body causing poisoning of various species of birds. The basis of the toxic action of diazinon is the ability to block the enzyme acetylcholinesterase. As a result, acetylcholine is accumulated in cholinergic synapses, excessive stimulation of the nerves and muscles is noted, and in the future, a violation of the normal passage of nerve impulses develops. Complex research was carried out of Domestic Turkeys (Meleagris gallopavo) in which spontaneous poisoning with diazinon was recorded. Biochemical examination of the serum was carried out using the biochemistry analyzer «Cobas Integra 400 plus». The activity of the serum acetylcholinesterase was determined by the Method of Hestrin, 1949. In the stabilized blood, the hemoglobin content was determined by the hemoglobin-cyanide methods, the number of red blood cells and leukocytes was counted in Gorjaev's count chamber and the leukogram - after microscopy of blood smears, painted according to the Romanovsky-Gimza methods. The breeding of birds was carried out using the Shores method. The organs were fixed in 10% neutral formalin, 96% ethanols and Carnoy’s solution. The histological sections were made using a sown and freezing microtome, stained hematoxylin and eosin. The histological study of the preparations and their photographing was performed using microcope Leica DM 2500, and camera Leica DFC 450 C., Application Suite Version 4.4.0. Clinically ill turkeys poisoned by diazinon showed oppression, tremor and paresis of wings. Later, the coordination of movements was disturbed: sick birds fell on their backs, marked swimming movements of the pelvic limbs, cramps and spastic contractions of the limb muscles. From the oral cavity was allocated a rare mucous mass. After acute attacks and spastic contractions of the muscles, muscle weakness developed. In the terminal periods of the disease, there were also spasms of various muscle groups, paralysis, difficulty and frequent breathing accompanied by wheezing, cyanosis of the skin. During the conducted biochemical examination of serum, a marked decrease in the level of acetylcholinesterase, an increase in the level of AST, cholesterol and uric acid was observed. In the pathoanatomical study, expressed discirculatory processes in the form of acute congestive hyperemia, stasis, perivascular edema and hemorrhages, as well as necrotic changes in cardiomyces, hepatocytes, nephrocytes and brain neurons were found. Quality positive reaction on diazinon was received as a result of the bird crop content research by the method of thin-layer chromatography paper manifestation of iodine bismuth.