The present research project was designed to determine the hematologiacal values in infected broiler flocks with hydropericardium syndrome from January to June, 2012 in order to adjoining areas of Hyderabad Sindh. A total of 72 containing population 96, 500 broiler chicken were surveyed to observe for hematological variation during the study period. Only 30 [41.66%] flocks were found affected with Hydro pericardium syndrome. Out of these flocks, the incidence of syndrome was recorded as 5.4% during the month of January, 7.41% in February, 10.8% in March, 13% in April, 15.1 in May and 12.8% during the month of June. The hematological studies were conducted in infected broilers with hydropericardium syndrome and found increase in white blood cells [WBC] from 14.500 +/- 2.298 to 25.820 +/- 844.00 and concentration of erythrocytic sedimentation rate [ESR] from 2.340 +/- 0.89 to 3.458 +/- 0.291. Amongst leukocytic count, showed marked increase with neutrophils and relative decrease of lymphocytes from 69.360 +/- 0.152 to 55.480 +/- 2.132, monocytes 4.660 +/- 0.598 to 3.340 +/- 270, eosinophils 1.496 +/- 0.204 to 1.004 +/- 0.097 and basophils 0.878 +/- 0.55 to 0.734 +/- 0.067 in infected birds