Currently, professionals and academics of non-formal education in Indonesia have began to question the competences of the non-formal education instructors. Non-formal education is a profession that requires knowledge (subject-content area), skill (ability to deliver content in regard to the needs of society) and programme content (the content appropriate to the condition of learners). This article mainly introduces a discussion on the Andragogical Content Knowledge in the field of non-formal education, in relation to the improvement of the instructor's competences, the author emphasises understanding the content since it is content which is the basis for any intended learning. Understanding content can lead to the development of the required character, knowledge, skills, and insightful reasoning needed in the learning process. Without the Andragogical Content Knowledge, teaching in non-formal education will become an everybody's area of specialization. Given the recent government interest in tutor/instructor competences for the non-formal education within Indonesia, this article focuses on "Andragogical Content Knowledge" as one way to contribute to the professionalisation of non-formal and continuing education in the country.