Since stakeholders of construction projects do not have full awareness about conditions, obligations, and terms of contracts or do not act upon them, problems can occur during the spam in which the project if carried out or after its finalization which leads to various claims. These claims prevent construction projects from completing and cause delay in delivery of projects or increase project cost and duration. This research investigates claims and proposes methodologies for their prioritization and management. Due to the similarities of construction projects in all over the world, this research could be found applicable in other construction projects. This research was performed based upon a statistical sample of 117 participants in construction industry and the data was collected through questionnaires. Related factors were categorized in 6 groups, consisting of: employer related conditions, factors related to contractors, subcontractors, contract documents, contractual relationships, project conditions and other factors. The questionnaire's reliability was evaluated by Cronbach's alpha and reliability of the questionnaire was confirmed. After analyzing the collected data from Friedman test, it was shown that the most important factors which have an effect on claims are: offering contractual price less than minimum tender price, contractor's financial problems, lack of materials and their inflated prices. Finally, as a result of this research, recommendations were provided for reducing claims and preventing them from occurring on construction industry. Limited research exists on this subject. Moreover, a remarkable flaw with previous studies has been a lack of appropriate questionnaires. This study had been promoted according to field studies of authors.