Introduction: There is global support for the teaching of cardiopulmonary resuscitation (CPR) in schools, and teachers are expected to play a leading role in a medical emergency. For effective resuscitation, retention of CPR knowledge after training is paramount. This study aimed at assessing the retention of CPR knowledge among student teachers at pre-, post-immediate, 8th-, and 14th-week post-training. Method: A quasi-experimental study using non-probability convenience sampling was conducted to select 41 respondents from the Department of Physical and Health Education, Faculty of Education (UiTM). A validated American Heart Association's 2015 Basic Life Support (BLS) multiple-choice questions (MCQ) were utilised to measure the retention of knowledge among the participants. Results: This study demonstrated a significant lack of CPR knowledge during pre-test with the mean scores of M=8.02 despite half of the participants had prior knowledge in CPR. Nevertheless, the paired t-test revealed a significant improvement in the post-scores following the intervention at M=16.20, t(40) = -18.56, p < 0.001, and d=3.91. The one-way RM-ANOVA results showed a decline in the retention rate at the 8th week (M=13.06; p < 0.001) and an improvement at the 14th weeks (M= 5.74; p < 0.001). Conclusion: The knowledge of CPR among the student teachers following the intervention program was appropriate, but the deterioration of retention suggested that all student teachers should undergo comprehensive routine CPR courses to avoid the immediate loss of CPR knowledge and skills. The governing bodies in Malaysia should implement CPR training as part of the curriculum for teachers.