Inter-organizational communication plays an important role in promoting strategic collaboration among firms. It can improve productivity and increases collaboration among employees. In this paper, we present an empirical study to measure the role of inter-organizational communication on efficiency among administration employees who work for one the oldest banks in Iran, Bank Melli Iran. The study uses 380 full time employees who work for 28 different administration divisions of this bank. The survey uses a questionnaire consists of 19 questions about inter-organizational communication and 25 questions about efficiency of employees. The reliability of the survey has been approved using an initial survey and Cronbach alpha was calculated as 0.87, which is well above the minimum acceptable level. The result of our survey confirms there is a meaningful relationship between inter-organizational communication and efficiency of all administration employees who work for this bank. There is also a meaningful relationship between age and efficiency and the maximum efficiency belongs to people aged 31 to 40. According to our survey, men have more inter-organizational efficiency than women do. The result of our survey also confirms that positivism impacts more than other factors on efficiency. Among five effective factors, empathy has the most impact and responsiveness 6 efficiency dimensions.