Work zone safety has become a very serious concern in traffic management over the past several years in Florida. The disturbance of construction/ maintenance activities on normal traffic may result in traffic conflicts, crashes, and even severe injuries. A clear understanding of the characteristics of work zone crashes is necessary to address the existing safety problems in work zones. In this paper, an injury severity model, utilizing the Ordered Probit Regression, was developed based on the history work zone crash data collected in Florida, to investigate the factors contributing to injury severity in work zones and to evaluate the impacts of the contributing factors. These factors include roadway geometric design, environment, traffic, and vehicle/driver characteristics. The results are valuable for developing appropriate countermeasures to reduce the injury severity of work zone crashes.