The purpose of this paper was to explore the language teachers’ attitudes towards teaching English grammar. In addition, this study compared the teachers’ beliefs and their actual behaviours in the class. The “Action Theory” was chosen regarding this issue. It was investigated if there was any compatibility between their beliefs and practice or not and in case of incompatibility, the subjects were aware of it or not. This paper also tried to explore the reasons of this incompatibility as well as to find out the factors that influenced the teachers’ actual behaviours in the class. The present study is a case study done in a semi-government language centre in Mashhad, Iran. Three female language teachers were selected as subjects for this research. To identify the language teachers’ attitudes towards teaching English grammar, a series of observations was done. And also, some interviews with three English teachers were planned to make known their attitudes towards teaching grammar. The Constant Comparative Method (CCM) was used to analyze the data obtained from observations and interviews. The findings of this study revealed that sometimes there was no compatibility between beliefs and actual behaviours. Most of the time, teachers were not aware of this incompatibility.