This paper investigates the potential impact of external factors on bid/no-bid decision for supervision consultant service on construction project in Hanoi, the capital of Vietnam. The data used in this study are secondary data taken from annual reports and sourced from the Department of Public Procurement, Ministry of Planning and Investment in Hanoi. Besides, to identify the impact of external factors on bid/no-bid decision for supervision consultant service on construction project in Hanoi, the study collected data from 272 qualified questionnaires from bidders doing business in Hanoi. Cronbach’s Alpha, EFA and regression model are used to explore the impact of each independent variable on bid/no-bid decision for supervision consultant service on construction project. The results show that three external determinants, including Project characteristic (PC), Legal codes (LC) and Competition (C) are affecting bid/no-bid decision for supervision consultant service on construction project in Hanoi. Among them, Project characteristic (PC) and Legal codes (LC) have positive relationships with bid/no-bid decision for supervision consultant service on construction project, whereas Competition (C) negatively affects bid/no-bid decision for supervision consultant service on construction project. It means the more contractors actually participate in a bid, the less bid/ no-bid decisions are made.