The primary objective of this work was to study the effect of tylosin on the honeybee larvae blood cells. Honeybee colonies were treated with a solution of tylosin. Larvae blood samples were collected and pulled directly onto glass and examine with 1250x microscope. In mostly the blood cells count were decreased except in prohaemocytes and oenocytes, in both treatments factors (time and larvae instar). The third day after treated with tylosin showed the highest amount of Oenocytes (12.67±4.04) in the third instar. While the lowest amount ((5.67±3.21) was recorded in the control. The Oenocytes cells in the second larvae Instar were increased and reached 10.67±2.31 while the control amount was 5.67±3.21. The results showed that, tylosin has strong effect on the blood cells count. And may be decreased the honeybee immunity.