Seijo Gakuen Junior High School and High School (成城学園中学校高等学校, Seijō Gakuen Chūgakkō Kōtōgakkō) is a private junior high and high school in Setagaya, Tokyo, operated by the Seijo Gakuen institute.

The Seijo Junior High School and separate Senior High Schools for boys and girls were established during the 1920s.

Following the 1949 education reforms, the system was restructured and the coeducational Seijo Gakuen Junior High School and High School was opened in 1950 while the tertiary education provision became a junior college, later obtaining university status.

The former girls' school did not have a prescribed uniform, a tradition which continues to this day, although they do have to abide by a general dress code.

Boys continue to wear the blazer and slacks.