Introduction: This study aimed to determine influenza vaccine coverage and evaluate the knowledge, attitudes and practice about influenza and vaccine of health care workers in Tehran, Iran. .9 % (range, 45% to 62%). Most HCWs (80.6%) had received an influenza vaccination in the past, and 65.4% intended to receive vaccination in the coming year. The main reason given for being immunized was the effectiveness of the influenza vaccine (51.4%). The main reason given for not being immunized was concern about adverse effects (23.1%). The knowledge score for the 35 items ranged from 0 to 34 (mean 17.37). Mean knowledge scores differed between educational levels. There was no significant difference in mean knowledge scores between females and males (P > 0.05). Independent variables (age, sex, marital status, having children aged ≤ 16 years, educational level) were not significant predictors of taking influenza immunization. Conclusion: Despite the high coverage rate of influenza vaccination in our study, we would expect a higher rate because of free vaccine availability. The results indicate the need for on-going education of influenza disease among HCWs to increase vaccination rates.