Several studies have examined the impact of both gender mixed groups and collaborative learning on the process of language learning. Some studies found that females were better than males whereas others showed that males were better than females. As for collaborative learning, most studies have shown that this type of learning improves and accelerates the process of learning. The present study intended to investigate (1) the effect of gender mixed groups on learners’ interaction in reading comprehension, and (2) the influence of collaborative learning activities on learners' achievements. In order to achieve these goals, 45 male and female high school students from Benghazi, Libya were divided into three groups. Each group included 15 students. One group (GIRLS GROUP) contained only girls; the second group (BOYS GROUP) included only boys whereas the third group (MIXED GROUP) was a mixture of both girls and boys. They were all taught by the same instructor in order to emphasize equality of teaching. The treatment lasted for five weeks, two hours a day, three days a week. Instructional tasks based on collaborative learning techniques and activities were provided to the students. A pre-test and post-test design was utilized in this study. Regarding the effectiveness of gender mixed groups on reading comprehension , the results revealed that Group (GIRLS GROUP) achieved the best results. For the influence of collaborative learning techniques, the findings showed remarkable development in the students’ achievements when using collaborative learning.