The authors investigated the differences in using problem decomposition and problem recomposition between dyads of engineering experts, engineering seniors, and engineering freshmen. Participants worked in dyads to complete an engineering design challenge within 1 hour. The entire design process was video and audio recorded. After the design session, members participated in a group interview. Video and audio data were transcribed, segmented, and coded to make comparisons. Results show differences between engineering experts, seniors, and freshman in design thinking. Students tend to use depth-first decomposition, and experts tend to use breadth-first decomposition in engineering design. The results also show that students spend less cognitive effort on the problem-definition stage than engineering experts.