This study examined the effects of technology‐based scaffolds that were composed through the use of the seven‐stage, problem‐based learning strategy on knowledge construction in a problem‐based online asynchronous discussion. In a quasi‐experimental setting, 60 students in an undergraduate Instructional Technology and Material Design course were assigned to one of three groups. In one group, students posted messages using a prescribed set of message categories. Using the same message categories, another group completed their messages using suggested sentence openers. A control group received none of the above mentioned scaffolds. Using a multi‐method approach (content analysis, measurement of learning performance), the research results showed that technology‐based scaffolding in a problem‐based online asynchronous discussion improves students' task orientation and leads to more task‐related learning activity. Furthermore, using both message labels and sentence openers, which were composed through the use of the seven‐stage problem‐based learning process theoretical framework, offers an effective strategy for encouraging more elaboration and higher cognitive discourse.