The purpose of this study was to explore the effects of scaffolding strategies on pre-service teachers’ reflective learning competency and attitude toward Self-Regulated Learning in Design Thinking-based online collaborative learning environments. To carry out this study, an experiment was conducted with 99 pre-service teachers who took the classes of Educational Technology-related courses in Busan Metropolitan City for 7 weeks. Also, this study verified the data collected through pre- and post-tests using multivariate covariance analysis(MANCOVA). The main results of this study are summarized as follows. First, there were significant differences in the means of the pre-service teachers’ reflective learning competency according to the scaffolding strategies. Especially, in the task-supported scaffolding group, ‘intensive reflection’ among the sub-factors of reflective learning competency showed a significant increase in the means. Second, in the case of the attitude toward self-regulated learning, there were significant differences between the three groups according to the scaffolding strategies treatment. In addition, it was founded that in the two of three sub-factors for attitude toward self-regulated learning, there were significant differences between the groups. Based on these results, this study suggested that instructors‘ specifically cognitive support has positive effects on the reflective learning competency and attitude toward self-regulated learning in the online collaborative learning environments combined with innovative instructional methods such as Design Thinking. Also, it emphasized the importance of the effective scaffolding strategies type and the necessity for concrete instructional design for pre-service teachers to support pre-service teachers’ ill-structured problem-solving processes in online collaborative learning environments.