This study was conducted to examine in depth the influences of the Covid-19 pandemic on the resource systems of mathematics teachers. This qualitative study is based on the documentational approach to didactics and is a case study conducted with two secondary school mathematics teachers teaching in the 7th grade. The research was limited to the subject of equations and equalities. Reflective analysis was used as a data collection method in this study. The data were obtained from the participating teachers in two stages, pre-pandemic and pandemic periods. Data in the first stage, which included the pre-pandemic period; consisted of the schematic representation of resources system for the face-to-face education period of the equations and equalities subject before the beginning of the online education and the semi-structured interview conducted before the online education of the subject started. The data of the second stage including the pandemic period, were obtained through the schematic representation of resources system prepared by the teacher at the beginning of the online education, and the video and audio recordings of the lessons in which the teacher taught the equations and equalities unit in a certain class with online education during the pandemic period. In the first part of the data analysis, the data obtained from the teachers in the prepandemic period were subjected to content analysis and the resources systems of teachers in face-to-face education was revealed. As a result of the examination of the schematic representation of resources systems prepared by the teachers in this section for the face-to-face education period and the analysis of the interview data, two themes, "General Habits" and "Special for Face-to-Face", were reached. In the second part, the data obtained from the teachers during the pandemic period were subjected to content analysis, and the teacher's resources systems in online education was revealed and two themes were reached: "General Habits" and "Special for Pandemic". When the resources systems of the teachers for the period in face-to-face education was compared with the resources systems for the pandemic period in the third section, the change in the documentation systems of the mathematics teachers during the pandemic was also revealed in detail. The results revealed that the duration of completing the unit has changed during the pandemic period, the variety of sources used did not change, but the type shifted from printed sources to z-book applications and benefited from much more technological tools than face-to-face education.