Objectives: This study aimed to evaluate the effectiveness of Basic Life Support (BLS) training on the knowledge and performance of intermediate students from a rural area. Methodology: A quasi-experimental study with pretest, posttest, and followup phases was conducted at a private sector high school. Non-probability purposive sampling was used to select participants, consisting of 11th and 12th-grade students with low to moderate levels of BLS knowledge, as assessed by a structured questionnaire. The BLS training, lasting three hours, included a PowerPoint presentation and hands-on practice. Data were collected from 80 participants at three stages: pre-test, post-test, and a follow-up test three months after the intervention. Participant performance was evaluated using the American Heart Association checklist. Data analysis was performed using SPSS version 25, with Friedman's ANOVA applied for inferential statistics. Results: Initially, 95% of participants had a low level of BLS knowledge, with a median score of 3. Post-intervention, knowledge significantly improved, with a median score of 6.5 and 37.5% of participants achieving a high level of knowledge, while 30% reached a moderate level (p-value <0.0001). However, knowledge retention declined after three months, with a median score of 4.0 (p-value <0.0001). Previous knowledge of CPR was significantly associated with improved post-intervention knowledge scores (p-value = 0.03). Conclusion: The BLS training significantly enhanced participants' knowledge and performance. Nonetheless, there was a notable decline in knowledge retention over time.