Guided by Activity Theory framework, this study tends to uncover prominent contradictions in the activity systems in which non-native English as a Foreign Language (EFL) grammar teacher cognition operates. The study attempts to fill the existing research gaps, as there are visible gaps in the literature to address the problem from this angle. To this end, the study used a mixed methods design, employing a teacher belief questionnaire and triangulated by a structured classroom observation checklist. The questionnaire was administered to 132 teachers, selected through stratified random sampling, while eight teachers were observed multiple times, based on purposeful sampling. The results of the study revealed several contradictions in the activity systems of EFL teacher cognition in grammar teaching. Weak teacher cognition caused by these contradictions contributes to the low proficiency level of their students. This research has practical implications and offers recommendations to enhance EFL teacher cognition in the area of grammar instruction.