Firms in the construction industry worldwide are faced with increasing pressure to integrate sustainability into their business strategies. However, there are still barriers that prevent firms to implement environmentally sustainable practices. The aim of this study was to address this problem in the framework of the construction industry of the United Arab Emirates. The methodological approach involved interviews followed by a structured questionnaire to collect data from 90 firms in order to empirically (1) identify the barriers, (2) examine whether the barriers in ISO 14001 certified firms differ significantly compared to those in non-ISO 14001 certified firms, and (3) examine whether the barriers vary significantly depending on firm size. According to the analysis of results, 15 barriers were identified. The top three barriers are economical benefits placed above meeting environmental sustainability requirements, lack of knowledge management, and insufficient support from policymakers. The results also showed no significant difference between firms adopting ISO 14001 and firms not adopting ISO 14001 in terms of the importance of each identified barriers, and the barriers do not vary significantly depending on firm size. These findings could guide managers and policymakers in construction firms interested in implementing environmentally sustainable practices in the UAE and firms operating in the same environment worldwide.