This study examines the direct effect of strategic agility on sustainable competitive advantage in the big and medium-sized manufacturing companies operating in Yemen. A total of 227 out of 554 of companies were surveyed using a stratified random sampling technique. The questionnaire was sent to the heads of companies and their deputies. Structural equation modelling technique CB-SEM (AMOS) was used to analyze data and test the hypotheses of the study. The findings revealed that strategic agility has a significant and direct impact on sustainable competitive advantage on how the big and medium-size companies can improve their competitiveness such as by improving their chance of survival in a very resource-constrained market. The questionnaire was sent to the heads of companies and their deputies.