Abstract Study Title: The Effect of Using Blended Learning on Learning Some English Grammar among The Students of The English Language Department at King Khalid University and Their Attitudes Toward It. Study Aims: The study aimed at: 1. Identifying the effect of using blended learning on learning English grammar at the levels of knowledge, comprehension, application, and all the three levels. 2. Identifying the students' attitudes toward using blended learning in learning English grammar. Study Questions: 1. What is the effect of using blended learning on learning English grammar among the students of the English Language Department at King Khalid University ? This question is followed by the following sub-questions: 1. What is the effect of using blended learning on learning English grammar at the level of knowledge? 2. What is the effect of using blended learning on learning English grammar at the level of comprehension? 3. What is the effect of using blended learning on learning English grammar at the level of application? 4. What is the effect of using blended learning on learning English grammar at all the three levels? 2. What are the students' attitudes toward using blended learning in learning English grammar? Study Methodology: The study followed the Quasi-experimental design with two groups; one is set as an experimental group and the other as a controlled group. Study Sample and Population: The study population was all students studying 'Grammar 2' course in the departments of English at King Khalid University. Whereas the study sample was fifty students studying in the Department of English at the College of Science and Art at Mohayil Governorate. Study Tools and Materials: The researcher used an achievement test, an attitude scale, a teacher guide and a student guide. Statistical Methods: The researcher used Mean, Standard Deviation, Cronbach's Alpha and Analysis of Covariance (Ancova). Study Findings: 1. There are significant statistical differences at the level of (0.05) between the posttest mean scores of the experimental group and the controlled group on the levels of Knowledge, comprehension, application and all the three levels, in favor of the experimental group. 2. There are significant statistical differences at the level of (0.05) between the postand pre-attitude scale, in favor of the post-attitude scale. Study Recommendations: 1. Blended Learning should be emphasized in teaching English in general, and in teaching English grammar in particular. 2. Universities staff, teachers and students should be trained on using blended learning, and be introduced to the different types of blend in education and the systems of e-learning management including the Blackboard. 3. Curricula should be planned and designed to match the immersion of technology in education. Attention should be paid when introducing a new method or strategy in the process of teaching and learning.