Introduction: Studying organizational culture acts as a tool for gathering information, and enables managers to compare work groups to prioritize problems and identify staff understandings and expectations to improve the gap between current and optimal situations. This research was aimed to study organizational culture in Hashemi Nezhad Hospital in Tehran based on Denison Model, to evaluate four aspects, as, Involvement, Consistency, Adaptability and Mission.

Methods: This is a Cross- Sectional study carried out in summer 2009. The research population are comprised all employees in Hashemi Nezhad Hospital, and the sample 130 employees selected through Randomized- Stratified sampling. Data are collected by Standard Denison Questionnaire and the analyzed by SPSS software, t-test and ANOVA tests.

 Results: The majority of employees (%72) evaluated organizational culture situation as suitable. The hospital gained the highest score concerning involvement and the lowest in consistency. The scores gained by the hospital in four main cultural aspects were medium level and above. The highest mean of organizational culture found for Team Orientation, 4.24 and the lowest mean was related to Coordination and Integration, 3.24. But totally most criteria were acceptable.

Conclusion: The organizational culture of this hospital was found in acceptable level, which will pave the way for successful changes and can help managers to predict change prioritize systematically and set strategies for successful implementation of management techniques and process.