As one of the recent and motivating teaching methods, this research aimed to study team teaching as its focus. The study investigated any significant effect of team teaching on English as a Foreign Language (EFL) Iranian learners’ grammar. Two classes of 25 learners (Experimental and control groups) were held. In these classes, 10 grammar tenses were chosen by the institute through learners’ weaknesses, such as present simple, present continuous, past simple, past continuous, and perfect tenses. Two teachers participated in this study, one as the main teacher responsible for teaching the materials and the assistant teacher responsible for doing the activities, answering learners’ questions, checking learners’ homework, and giving feedback to them. A grammar test was administered as the pre-test and post-test for both groups. The pre-test was taken before the 10 sessions and the post-test was taken after finishing the 10 sessions. The researcher analyzed both groups’ scores and the results indicate a significant positive effect of team teaching on the experimental group, signifying that the study’s treatment was statistically and significantly effective. Moreover, no significant difference was found between boys and girls in students’ grammar success as a result of team teaching.