In this study, the effect of blended learning environment using DynED on student achievement and attitudes towards English course was determined as the aim of this research. Quasi-experimental design with pretest-posttest control group which is defined as a two-factor mixed design was used. Study group of this research consisted of 40 -- 4th grade students who are studying at an elementary school in 2018-2019 academic year. The research data were collected by using academic achievement test (Kr20 = 0.91) and attitude scales towards English Lesson (Cronbach Alpha between 0.77 and 0.93). In the experimental group, the English lesson was taught in a blended learning environment using the DynEd platform. The control group students only participated in English courses given in the school environment. Data were analyzed using arithmetic mean, standard deviation, and t analysis. As a result: Students in both experimental and control groups have very high attitudes towards English course. The blended learning using DynEd in English Course contributes significantly to the academic achievement of students compared to the traditional method but there is no contribution significantly to the students' attitudes towards English course.