This study aims to quantify the barriers to ECI implementation in Nigeria. Barriers to ECI implementation were identified through an in-depth review of existing literature. These barriers were then contextually customized through a pilot test and presented as a hypothesized model. Questionnaire survey data were elicited from 179 construction professionals in Nigeria. Partial least square structural equation modelling (PLS-SEM) and fuzzy synthetic evaluation (FSE) were used to statistically validate the final model of the barriers to ECI implementation. The analyses revealed that the underlying barriers hindering ECI implementation in Nigeria are a lack of collaboration and inadequate preparation. The analyses also revealed that the underlying barriers to ECI implementation in Nigeria are moderately critical. Furthermore, the study findings suggest that project stakeholders should invest in early-stage planning, provide training to enhance stakeholder engagement and decision-making, implement a structured coordination framework, use digital tools and foster open communication to overcome barriers to collaboration and preparation in ECI implementation. These findings can provide practical strategies to improve ECI implementation in Nigeria and other developing countries. This study addresses a knowledge gap by focusing on quantifying the critical barriers to ECI implementation in Nigeria.