Delayed graduation among graduate students constitutes an educational issue that influences individual career development; however, the severity of this issue has increased over time. To understand the effect of delayed graduation from the student perspective, this study adopted the theory of belief–action–outcome to examine the correlations among personalities, overconfidence, academic procrastination, and frequency of seeking advice—all of which influence graduate students’ study duration. Therefore, this study adopted convenience sampling to administer questionnaires, to which 236 valid responses were collected. After the reliability and validity test, confirmatory factor analysis with structural equation modeling was performed. The results suggested that extraversion is positively related to overconfidence and academic procrastination, neuroticism is negatively related to overconfidence and academic procrastination, overconfidence and procrastination are negatively related to the frequency of seeking research advice, and the frequency of advice seeking was negatively related to study duration. According to this study, professors guiding graduate students with their thesis should consider their different personalities and offer more frequent seminars for counseling.