Success of an organization, more than anything else, depends on the human resources. Behavioral science emphasizes that organizational success mainly depends on efficient use of human resources. It is especially true in organizations such as libraries. To promote “positive thinking” ” among the staff of libraries and information centers, training courses should be arranged. To improve librarians' efficiency, these training courses should be held within the framework of an overall continuous program. In this research, the degree of “positive thinking” of librarians in 13 central university libraries affiliated to the Ministry of Science, Research and Technology (MSRT) in Tehran was assessed. Using random stratified sampling and random digits’ table, 144 employees were selected from among the total 218 employees working in these libraries as sample population. An author made checklist, which was based on Ingram and Wisnicki’s 5-factor questionnaire and consisted of 30 items, was applied as data-gathering tool. Descriptive survey was applied and the results showed the average values for positive daily functioning, positive self-evaluation, others evaluation of self, positive future expectations, and self-confidence were 3.737, 3.833, 3.965, 3.94, and 3,555 respectively. Among the five options of always, often, limited, sometimes and never, which are five options of Liker’s questionnaire, the tendency was toward choosing either often or always.