Currently, smartphones are becoming a popular device of M – learning (or Mobile learning –learning by accessing teaching content via mobile devices), especially in the context when schools are closed because of the pandemic. Our study aims to determine factors affecting the acceptance of smartphones by 285 high school math teachers in Binh Duong Province and Ho Chi Minh City. We used a simple linear regression model to analyze the influence of explanatory variables on the acceptance of smartphones as a teaching tool. The results show that confidence in using math teaching software, perception of the feasibility of using math teaching software, and gender affected the teacher’s acceptance of smartphones. In addition, the Chi-square test results show that there is no significant difference between the groups that accept, hesitate, or do not accept smartphones in teaching, while the acceptance rate is the highest.