Nationalism among the youth is declining. This study aimed to determine the significance of perceived knowledge and attitudes on history as determinants of learner's sense of nationalism. A predictive correlational research design was employed, utilizing a survey questionnaire administered to 331 senior high school students identified through cluster sampling. Data were analyzed using regression analysis. The findings conclude that only attitudes, not perceived knowledge, significantly influence learners' sense of nationalism. Tajfel’s Social Identity Theory was partially affirmed. Based on these findings, future research to explore additional variables not included in this study to explain the 70.2% variance in the sense of nationalism variable and relevant policies on fostering a sense of nationalism is recommended.