This study investigated the effectiveness of mnemonics in teaching Araling Panlipunan 9 on students’ written assessment scores. It used a one-group pretest-posttest design, a quasi-experimental design of the quantitative research methodology. The study was conducted at a National High School in Apayao, Philippines. Purposive sampling was used to select 40 Grade 9 students as participants. The researchers used a validated assessment instrument adopted from the Department of Education modules. The results showed that the students improved their scores significantly after using mnemonics in teaching, as indicated by the increase in the mean average score, the rejection of the null hypothesis, and the positive correlation between mnemonic usage and performance. The study recommended continuing to use mnemonic techniques in teaching Araling Panlipunan 9, providing remedial support to low-performing students, and promoting active student engagement in the learning process.