Conditions that occur in the world of education involve learning that is required to take place to achieve predetermined competency targets. Substantially the direction of distance learning must really be an alternative that can support education. The Microsoft Teams application is one of the learning applications that can be applied to online distance learning during the covid-19 pandemic, with the application of the Microsoft Teams learning application, teachers can increase students' interest/motivation in learning while they are at home. This study aims to explain the implementation of mathematics learning, the application of the Microsoft Teams application, and the obstacles encountered by mathematics teachers using the Microsoft Teams application in learning mathematics. This type of research uses qualitative research with a case study approach. The subjects in this study were 1 mathematics teacher and 5 students in class XI IPS 5 whose learning was done through the Microsoft Teams application. This research trial was in class XI IPS 5 with 35 students. Data collection methods used interviews, observations and take notes. The data analysis used is the Analysis Interactive model from Miles and Huberman. The results show that 1) learning mathematics during distance learning using the Microsoft Teams application at Perintis 2 Senior High School Bandar Lampung can still run smoothly, but this condition can also affect teacher interaction and students in learning. 2) the teacher has been able to apply the Microsoft Teams application in learning because there are media that support the teacher during online learning, the learning media in question are the meter, quiz, padlet and group room. The obstacles encountered by the teacher in learning mathematics by implementing the Microsoft Teams application are mainly on the internet network so that students are quite passive in implementing mathematics learning. This finding leads to a recommendation for the government to develop learning media in the Microsoft Teams learning application so that it can improve student and teacher understanding in learning mathematics during distance learning.