Blended learning has been widely recognized as a valuable practice that contributes to students’ academic achievement. However, this mode of education is accompanied by constraining factors that influence students’ motivation in the process of learning and that influence their knowledge internalization. In this study, a qualitative inquiry was made into students who were enrolled in a blended learning course of English reading at a university in China during which self-assessment was required alongside learning. Through a case study approach and a thematic analysis of data sources (e.g., interviews with the students and their self-assessment journals), the study shows that blended learning benefitted but also challenged the students, while self-assessment helped them critically reflect upon their learning pace by identifying progress and issues, restoring their motivation to undertake blended learning and facilitating their knowledge construction. Ultimately, both students’ self-assessment and blended learning became relatively stable, with both practices individually benefiting the students, and formed a mutually feeding and interactive loop that benefited students holistically. The study concludes by assessing the pedagogical usefulness of synergizing blended learning and self-assessment to support students’ academic development.