This paper presents an empirical investigation to determine important factors influencing on getting competitive advantage on two construction firms, namely Keyson and Sazeh consultants in Iran. In this study, four variables of internal resources, personal characteristics of decision makers, demand conditions and market strategies/services are investigated. The study prepares a questionnaire consists of 19 questions in Likert scale and distributes it among 145 regular employees who work for these two firms. Cronbach alpha was calculated as 0.93, which was well above the minimum acceptable limit. The results of the survey have confirmed that while four issues influence on the success of the firms on getting competitive advantage, there were some meaningful difference between the effects of the factors.