Smartphones are widely used among high school students nowadays. With their constant use of this technology, they have become more dependent on it. This study assessed the extent of smartphone utilisation and the academic performance of the 195 junior high school students at a public national high school. Respondents were identified using stratified random sampling and were asked to answer a survey questionnaire assessing their smartphone utilisation during their math classes while their performance in the subject was determined using their First Quarter grades. The data gathered were treated using descriptive and inferential statistics. The results revealed that the respondents had very satisfactory performance and they often use their smartphones during their math classes. Smartphone utilisation has a negative negligible correlation with the student's academic performance in Mathematics. Furthermore, Smartphone utilisation has no significant relationship between the respondents' math performance. Hence, teachers are encouraged to monitor students' use of gadgets during their math classes.