International trades rely on robust supply chains. However, supply chains are vulnerable to disruptions. Before implementing lean construction, identifying construction supply chain vulnerabilities (CSCV) is crucial to avoid failure. Meanwhile, an unfavorable macro-environmental context (e.g., challenging economic and political situations) can potentially affect the behavior of CSCV. This paper aims to identify and prioritize CSCV under an unfavorable macro-environmental context in a real-world case and then analyze the changes in CSCV in a period coinciding with the Covid-19 outbreak. A literature review led us to extract 26 variables that were then prioritized using the responses from questionnaires distributed among 72 participants in the studied country. A descriptive statistical approach was used to analyze the results, which showed that unlike the normal contexts mentioned in previous studies, under an unfavorable context, such CSCV as "price and exchange rate fluctuations", "supply-demand volatility", "financial issues", and "political challenges" gained priority. Moreover, analyzing the changes in CSCV indicated that the studied construction supply chain has become more vulnerable in the mentioned period. Considering the identified CSCV, this paper suggests that managers focus more on tools such as the Last Planner System and value stream mapping when implementing lean.