Extensive studies have been conducted to diagnose and predict students' academic performance by analyzing a large amount of data related to their learning behaviors in a blended learning environment. But there is a lack of research examining how individualized learning interventions could improve students' academic performance in such a learning context. In this study, a quasi-experiment was designed to investigate the effect of an individualized intervention approach on students' course performance and learning behaviors in a blended course. Forty-nine Chinese tertiary students undertaking the course were randomly assigned into two groups -- the experimental and control groups. During the course, the experimental group received individualized interventions, while the control group received undifferentiated interventions. The data about these participants' learning behaviors were collected over 15 weeks. The results indicated that, compared with the control group, the experimental group showed significantly better academic performance, a higher level of learning motivation, attitude and self-efficacy, more active learning behaviors, and fewer passive learning behaviors. The control group revealed similar online learning time, but significantly more resource utilization and forum access. It is concluded that personalized learning intervention can effectively improve students' learning behaviors, attitude, motivation, self-efficacy, and academic performance in a blended learning environment.