Influenza pandemic was a global event in 2009 and intraschool transmission was its main spread method. The present study was designed to evaluate the absenteeism rate during the type A influenza epidemic. Four hundred and eight students from both a guidance school and high school in the Iranian capital were recruited in this retrospective study. The number of days of absenteeism, since the beginning of the school year until the end of the epidemic was recorded. Two hundred and thirteen students missed school during the disease epidemic because of related causes. In other words, 581 person day absences were reported during this period. The influenza pandemic has led to an increase in the absenteeism rate and may negatively affect the academic performance of the students. Teaching precautionary measures is an effective tool in reducing the number of days of sickness. (Contains 3 tables and 3 figures.)