Collaboration proves to be an effective way to facilitate students’ engagement and solve the mostly-mentioned problems of blended learning (BL). For collaborative BL, self-regulated learning (SRL), self-efficacy and engagement are frequently referred to in BL studies and represent key elements of effective BL. Furthermore, the interaction of these elements correlates closely with the performance of students. There have been few research attempts to draw synergies and explore the relationship among these key elements. To address this gap, data were collected through a questionnaire and records on LMS from 125 students in a Chinese university. Descriptive analytics show that students fully recognize the positive effects of collaborative BL. Correlation analysis and regression analysis find that self-regulated learning (SRL) is significantly correlated with all factors except workload. It is also a significant predictor of behavioral engagement. Therefore, SRL proves to be central among the essential BL elements. Emotional engagement is significantly correlated to and interact with multiple key BL factors. Specifically, emotional engagement is a significant predictor of behavioral engagement. The findings offer insight into the interactions of key elements of BL and provide practical implications for improving BL learning design.