<p>Smartphone distraction is a concern in university classrooms. However, the effectiveness of notification salience in reducing the impact of smartphone distraction on learning remains unclear. This study examined how external smartphone stimuli (i.e., notifications) and internal smartphone-related distraction (i.e., smartphone vigilance) influence students’ in-class phone use and learning performance. A quasi-experimental design was used to evaluate 84 Taiwanese undergraduates who were randomly assigned to groups with two different smartphone settings: notification revealed (NR) and notification hidden (NH). Using behavioral observations, self-report measures, and a performance test, we employed t-tests to analyze group differences in phone-use behaviors and learning performance. Partial least-squares structural equation modeling was used to examine the relationships among habitual phone use, smartphone vigilance, phone-use behaviors, mental effort, and learning performance under different smartphone settings. The results revealed that smartphone settings moderated the relationship between vigilance and phone-use patterns: When experiencing heightened smartphone vigilance during learning, students in the NR group exhibited more frequent checking behavior. Those in the NH group, meanwhile, tended toward longer duration per use, referring to extended time spent on each smartphone session. Both use patterns negatively affected learning performance by increasing mental effort, potentially explaining the absence of differences in performance between the groups. This study advances the literature by clarifying the distinct effects of external stimuli and internal distraction, highlighting that merely hiding notifications may be insufficient to prevent distractions in classrooms where smartphones remain accessible. Practical implications of student self-control strategies and classroom smartphone policies have also been discussed.</p>