To help young students succeed in problem-based learning (PBL), researchers suggested investigating students' need for cognition (NFC), one's inclination to exert mental effort during learning. How one puts mental effort into a learning task is related to motivation. If motivated, students are more likely to engage in challenging tasks, put in more effort, and feel competent about what they are doing. This study investigated, through a mixed-methods design, middle school students' NFC, their motivation to learn, their learning performance, and the relationships among these factors as they engaged in technology-enriched PBL. The findings showed that NFC played an important role in students' learning. There were significant positive relationships among NFC level, intrinsic motivation both in general and in using PBL, and their learning performance. There were also significant differences in learning performance among the high, medium, and low NFC groups, showing that students in the high group performed better than their counterparts. However, the low NFC group gained more knowledge than their counterparts after using PBL. The study's findings were further substantiated by qualitative data, which provided nuanced insights that complement the quantitative evidence through detailed topic and sentiment analyses. Limitations of the study were also discussed.