Delay is a common problem of the construction sector and it is one of the major reasons of claims between project participants. Systematic and reliable delay analysis is critical for successful management of claims. In this study, a delay analysis ontology is proposed that may facilitate development of databases, information sharing as well as retrieval for delay analysis within construction companies. A detailed literature review on construction delays has been carried out during the development of the ontology and it is evaluated by using five case studies. The delay analysis ontology may be used for different purposes especially to support decision-making during risk and claim management processes. It may enable companies to create their own databases, corporate memories and develop decision support systems for better analysis of delays.