The use of history of mathematics in mathematics teaching is widely recognized. However, to date, its effectiveness has not been systematically evaluated. An experiment was conducted with the topic on Pythagorean Theorem at Secondary 2 under the framework of “intended–implemented–attained curricula.” The duration was three weeks and the effectiveness of the class under experimentation was compared with a parallel one. A teaching capsule was designed to remedy the shortcomings of current practice of teaching the particular topic as found in a pilot research. Pre-assessment and post-assessment of students’ attitude towards mathematics, enjoyment of learning in mathematics, learning motivation and mathematics self-concept were conducted at the start and at the end of the course. Their test scores were also collected. In the experimental group, these questionnaires were supplemented by a list of open-ended questions on how well they received the new way of teaching and how well they received the capsule (teaching material). Semi-structured interviews were also conducted on the teacher and six students from the experimental group on their perception of these three weeks of teaching and learning experience.