The integration of STEM education has been promoted to improve the quality of education in the 21st century, with its usage leading to emphasis on the factors influencing the intentions of preservice teachers. Therefore, this study aims to determine the factors influencing preservice teachers’ intentions, as well as the effects of gender and age on the implementation of STEM education. The Theory of Planned Behavior (TPB) was adopted to predict the relationship between knowledge, social influence, attitude, perceived usefulness, control, and behavioral intention (BI) of using STEM education among preservice secondary school teachers. A total of 30 item questionnaires on behavioral intentions were distributed to 201 respondents, with data being analyzed using the Structural Equation Model (SEM). The results showed that perceived usefulness had a positive significance, and a relationship with the attitudes of preservice teachers toward STEM education. Habit had a positive significance in influencing teachers’ behavioral intentions and implementation. Subjective norms did not have a significant correlation with BI and implementation. These results are recommended for providing solutions to analytical problems, and to successfully improve future learning through an educational approach.