Students and faculty from over sixty countries are represented at Seisen, with English being the main language of instruction.

"[4] According to Anne-Marie De Mejía, Seisen International School provides a specifically Christian orientation in its programmes.

[2] The school was founded in 1949 by Sister María Asunción Lecubarri from the Handmaids of the Sacred Heart of Jesus[3] in response to requests from United States Air Force families seeking an education for their children.

In 2013, a new futsal field was added to expand the ever-growing Seisen campus, as well as to provide further opportunities for physical exercise, including PE classes and extracurriculars.

The media center houses filmstrips, records, cassettes, maps, transparencies, and audiovisual equipment.