Diversification is one of the primary strategies adopted by construction companies. This strategy has both advantages and disadvantages. This study develops a fuzzy, multiple-criteria, decision-making model to determine the most appropriate diversification strategy for construction companies. The data required were obtained during face-to-face interviews, and fuzzy state and fuzzy alternative approaches were used. Consequently, the most appropriate diversification strategies for construction companies are highly diverse. Moreover, the most critical company data for monitoring the reasons for diversification, and the most important indicators for observing company data were identified.